RU2762564C1 - Method for preparation of aluminum hydroxide - Google Patents

Abstract

FIELD: chemical industry.

SUBSTANCE: invention can be used in the production of aluminum oxide adsorbents, desiccants, catalyst carriers and catalysts. To prepare aluminum hydroxide containing isolated lanthanum atoms, the product of rapid heat treatment of hydrargillite is crushed to particles with a volumetric average diameter of 5-25 microns, then hydrated by 0.3wt. %, nitric acid solution, filtered and washed from impurity sodium. The wet sediment is subjected to hydrothermal treatment in the form of a suspension in an aqueous solution of nitric acid and a lanthanum source. After drying, aluminum hydroxide is obtained with the general formula Al₂O₃⋅nH₂O, where n = 1.5-1.9, consisting of pseudoboehmite and a disordered χ-like phase of aluminum oxide at a ratio of these phases, wt.%: 60-95 pseudoboehmite, 5-40 disordered χ-like phase of aluminum oxide. Aluminum hydroxide contains isolated La atoms on its surface with a surface density of 2-50 atoms per 10 nm² surface and a ratio of Al atoms to La atoms equal to 50-10000, includes constitutional water, contains impurity Na in the range of 0.001-0.04 wt. %. The specific surface area after calcination at 550°C is 200-300 m²/g, the average pore diameter is 8-15 nm, the pore volume is 0.45-0.75 cm³/g.

EFFECT: invention makes it possible to increase the catalytic activity and selectivity of aluminum hydroxide, reduce the cost of obtaining it.

7 cl, 1 tbl, 7 ex

Description

The invention relates to methods for preparing aluminum hydroxide with a structure predominantly related to pseudoboehmite, and can be used in the oil and gas processing, petrochemical and chemical industries, in particular, in the production of alumina adsorbents, desiccants, catalyst carriers and catalysts themselves.

The starting material for the production of many alumina adsorbents, desiccants, carriers and catalysts is aluminum hydroxide with a pseudoboehmite structure, described by the general formula Al ₂ O ₃ ⋅nH ₂ O, where n = 1.5-1.9. There is also well-crystallized boehmite described by a similar chemical formula, where n = 1. The use of boehmite in the manufacture of adsorbents, drying agents, catalyst supports and catalysts themselves severely limited, since γ-Al ₂ O ₃ obtained by heat treating boehmite, characterized by low values of specific surface area and low pore volume, which makes further use ineffective.

Pseudoboehmite differs from boehmite in several characteristics, namely:

1) the presence of an excess amount of molecules of constitutional water in comparison with the stoichiometry of boehmite, which can be located both on the surface of particles and in the interlayer space of the layered structure of "boehmite";

2) smaller crystallite size with a coherent scattering region less than 10-13 nm;

3) reduced to 400-420 ° C the value of the decomposition temperature of aluminum hydroxide to γ – Al ₂ O ₃ , which is due to an increase in the length of the hydrogen bond between the layers, which in turn depends on the size of the crystallites.

There are many different aluminum hydroxides with a pseudoboehmite structure used to obtain alumina materials, which are both pure aluminum hydroxide and containing various additives. Additives are introduced into the structure of aluminum hydroxide or on the surface of aluminum oxide, since supports based on aluminum oxide are currently not considered as an inert dispersed substance; on the contrary, the support on its surface has active centers of one nature or another, which have a rather strong effect on sorption and the catalytic performance of alumina, or catalytically active metals, when deposited on an alumina surface.

A common disadvantage of such aluminum hydroxides is their suboptimal chemical composition, which does not allow the preparation of supports with the required surface properties, as a result of which the adsorbents and catalysts based on them do not possess sufficient sorption or catalytic activity for the current level.

One of the ways to optimize the characteristics of aluminum hydroxides / oxides and products based on them is to introduce various elements, for example, lanthanum, or their compounds at the stage of preparation. The use of lanthanum compounds in small amounts in the preparation of aluminum oxides and hydroxides allows increasing the thermal stability of γ-alumina obtained by heat treatment during high-temperature processes, maintaining its textural characteristics during phase transitions during high-temperature processing, increasing the activity of catalysts based on it, increasing them resistance to decontamination.

There are many different methods for preparing aluminum hydroxides, both with and without additives of chemical elements. The most typical inventions are discussed below.

So, in [RU 1721990, C01F 7/02, 19.06.1995] aluminum hydroxide is obtained by hydrothermal treatment of gibbsite (hydrargillite) in the presence of metal hydroxides (Mg or Ca) at pH = 2-11 and a temperature of 80-200 ° C. The resulting mass is subjected to repulpation in water to obtain a suspension with a concentration of 5-20 wt. % and spray drying.

The disadvantages of this method include the absence of the stage of washing the starting material - gibbsite - from impurity sodium, which, in view of the peculiarities of the preparation, is always contained in gibbsite in large quantities. As a consequence, the aluminum hydroxide obtained by this method contains at least 0.3 wt. % sodium, which excludes the use of this material for the production of most of the known catalysts, for example, hydrotreating, since sodium in this case acts as a catalytic poison. In addition, alumina synthesized from aluminum hydroxide obtained by the above method is characterized by a moisture capacity of no more than 0.35 cm ³ / g, which does not allow the use of such aluminum hydroxide in the production of catalysts, for example, by impregnation, namely, this method is obtained most of the modern high performance catalysts used in oil refining. In addition, metal hydroxides used in this method are converted into metal oxides during synthesis, which makes their use ineffective.

A known method of producing a powder of aluminum monohydroxide of pseudoboehmite structure, which includes thermochemical activation of gibbsite [RU 2558891, C01F 7/02, 08/10/2015]. The activation products are washed on a drum filter with a solution of ammonium nitrate with a concentration of 0.5-5 g / l at a pH of less than 7-8. The washed activation product is subjected to plasticization in a nitric acid solution at a pH of 3-4 and a temperature of 160-170 ° C. After that, water is added to the plasticization product until the ratio S: W = 1: (5-6), and the resulting suspension is subjected to spray drying at 140-170 ° C. The disadvantages of this method include the need for thermochemical activation of gibbsite, the absence of a lanthanum introduction stage, the use of an explosive substance - ammonium nitrate in the production, a large entrainment of a solid phase into the filtrate through the filter cloth of a drum filter, suboptimal chemical composition and surface condition.

A known method for producing powdered aluminum hydroxide [RU 2167818, C01F 7/02, 05/27/2001], which includes heat treatment of gibbsite in an air stream at 350-550 ° C, washing the resulting product from sodium and subsequent plasticization of the suspension with a concentration of solid heat treatment product 8- 15 wt. % and pH = 1-4 with a rise in the temperature of the suspension at the plasticization stage from 50 to 130-200 ° C at a rate of 10-25 ° C / h for 6-15 hours. The pH value of the suspension sent for spray drying varies in the range 4-10. The main disadvantages of the method are the need to adjust the pH with ammonia after the stage of plasticization; low moisture content of aluminum oxide obtained by heat treatment of aluminum hydroxide; suboptimal chemical composition and surface condition of aluminum hydroxide due to the absence of the stage of introducing lanthanum.

Closest to the proposed technical solution is described in [RU 2099135, B01J21 / 04, 20.12.97] a method for producing lanthanum-stabilized alumina - aluminum hydroxide. According to this method, aluminum hydroxide is synthesized from alumina powder obtained by rapid dehydration of aluminum hydroxide or oxyhydroxide and rehydrated in the presence of lanthanum compounds at a temperature of 95-100 ° C. Moreover, the use of a lanthanum nitrate solution as such a compound is preferable. Upon hydration of the product of rapid dehydration of gibbsite, a crystalline phase, called boehmite, develops. A solution of lanthanum nitrate is introduced at the stage of maturation of aluminum hydroxide in an amount corresponding to 5-10 wt. % based on lanthanum oxide in relation to the mass content of the original powder.

The main disadvantages of the method include the fact that the aluminum oxide powder obtained on the basis of such aluminum hydroxide at 550 ° C has a low specific surface area - 140-160 m ² / g, with a moisture capacity of 0.2 to 0.3 cm ³ / d, which limits its use for the production of adsorbents and most catalysts for oil refining, for example, hydrotreating. In addition, the lanthanum solution is consumed in significant quantities, and lanthanum itself is contained in the composition of aluminum oxide in the form of a separate chemical compound La ₂ O ₃ , which worsens the dispersibility of the metal on the surface and reduces the efficiency of its use.

The invention solves the problem of developing an effective method for producing aluminum hydroxide containing isolated lanthanum atoms.

EFFECT: obtaining by the claimed method of aluminum hydroxide, characterized by the presence of isolated La atoms on its surface, optimal chemical composition, optimal phase composition, optimal textural characteristics of pseudoboehmite powder calcined at 550 ° C, a given size of particle agglomerates.

Such aluminum hydroxide can be used in the oil and gas processing, petrochemical and chemical industries, in particular in the production of alumina adsorbents, desiccants, catalyst carriers and catalysts.

The production of isolated atoms on the surface is a powerful and attractive method with exceptional performance, resulting in dramatic cost savings and marked increases in catalytic activity and selectivity. Cost reduction is achieved due to the optimal use of the additional element, and an increase in catalytic activity and selectivity is achieved due to the availability of all isolated atoms during impregnation with an active component or directly during the catalytic reaction.

The problem is solved by the method of preparing aluminum hydroxide with the general formula Al ₂ O ₃ ⋅nH ₂ O (where n = 1.5-1.9), containing isolated lanthanum atoms, in which first the product of rapid heat treatment of hydrargillite is ground to particles with a volumetric average diameter of 5 -25 μm, then hydrated in a weakly concentrated solution of nitric acid, filtered and washed from impurity sodium, subjected to hydrothermal treatment in the form of a suspension in an aqueous solution of nitric acid and a source of lanthanum, and after drying, aluminum hydroxide is obtained with the general formula Al ₂ O ₃ ⋅nH ₂ O, where n = 1.5-1.9, additionally containing on its surface isolated La atoms with a size of about 0.1 nm, consisting in the chemical bond La-O-Al, with a surface density of 2-50 atoms per 10 nm ² surface and the ratio of Al atoms to La atoms equal to 50-10000; consisting of pseudoboehmite and a disordered χ-like phase of alumina; containing not more than 0.04 wt. %, but not less than 0.001 wt. % impurity sodium; characterized by a specific surface area of 200-300 m ² / g, an average pore diameter of 8-15 nm, a pore volume of 0.45-0.75 cm ³ / g in the case of heat treatment at 550 ° C and representing agglomerates of particles with a volume average with a diameter of 5 to 100 microns.

Lanthanum nitrate is used as a source of lanthanum in the form of crystalline hydrate or in the form of a solution.

Suspension of aluminum hydroxide is subjected to drying in a spray dryer at a temperature of the heat carrier gas 220-350 ° C.

As a result, aluminum hydroxide is obtained, which:

- additionally contains on its surface isolated La atoms with a size of about 0.1 nm, consisting in the chemical bond La-O-Al, with a surface density of 2-50 atoms per 10 nm ^{2 of the} surface and a ratio of Al atoms to La atoms equal to 50-10000;

- from the point of view of X-ray phase analysis, it consists of pseudoboehmite and a disordered χ-like phase of aluminum oxide in the following ratios, wt. %: pseudoboehmite 60-95, disordered χ-like phase of aluminum oxide 5-40;

- contains constitutional water in an amount of 22-25 wt. %;

- contains no more than 0.04 wt. %, but not less than 0.001 wt. % impurity sodium;

- characterized by a specific surface area S _beats 200-300 m ² / g, an average pore diameter D - 8-15 nm, a pore volume V - 0.45-0.75 cm ³ / g in the case of heat treatment at 550 ° C.

- represents agglomerates of particles with a volumetric average diameter of 5 to 100 microns.

The formation of isolated lanthanum atoms on the surface of aluminum hydroxide occurs during the hydrothermal interaction of the powder washed from impurity sodium ions by the rapid thermal treatment of hydrargillite and lanthanum ions contained in an aqueous solution of lanthanum nitrate. In this case, a chemical bond of the La-O-Al type is formed, and the lanthanum atoms themselves are uniformly dispersed over the surface of the aluminum hydroxide. After the hydrothermal synthesis, the suspension is spray dried, as a result of which an aluminum hydroxide powder with a given particle size and structure is predominantly pseudoboehmite.

The main distinguishing feature of the improved aluminum hydroxide in comparison with the prototype is the presence of evenly dispersed lanthanum atoms over the surface of the aluminum hydroxide. The fact that the ratio of the number of Al atoms to the number of La atoms goes beyond the stated limits, on the one hand, leads to uneven dispersion of lanthanum atoms over the surface of aluminum hydroxide, which worsens its characteristics, and on the other hand, prevents the formation of the La-O-Al bond.

The second distinguishing feature of the proposed method for producing aluminum hydroxide in comparison with the prototype is a set of stages of processing the initial reagent - a product of rapid heat treatment of hydrargillite (PBTOG), including its grinding, hydration, filtration and washing, hydrothermal treatment of the washed PBTOG product in the presence of a lanthanum source, and spray drying, ensuring the production of aluminum hydroxide with the characteristics listed above.

The achievement of the technical result is ensured by the following:

1. Use of the initial product of rapid heat treatment of hydrargillite with the required characteristics;

2. Using a set of actions according to the proposed method, the most important part being the introduction of a source of lanthanum at the stage of hydrothermal synthesis with strict adherence to the ratio of the number of aluminum atoms to the number of lanthanum atoms;

3. The use of spray drying to obtain agglomerates of particles of a certain size.

Below is a description of the proposed technical solution.

Take a sample of the product of rapid heat treatment of hydrargillite (PBTOG), which has a specific surface area of at least 200 m ² / g and meets the following requirements, wt. %:

- the proportion of hydrargillite (gibbsite), no more than 3;

- share of boehmite, no more than 10;

- the proportion of disordered χ-like Al ₂ O ₃ (X-ray amorphous or amorphous phase, or ρ-Al ₂ O ₃ ), not less than 87;

- the proportion of weight loss on ignition at 800 ° C, in the range of 6-10;

- the proportion of sodium oxide (Na ₂ O), no more than 0.3.

Either the CTA product (TU 2175-040-03533913-2007), obtained in a centrifugal drum-type reactor CEFLAR [RU 2264589, F26B7 / 00, 20.11.2005], or thermally activated aluminum hydroxide TGA (TU 24.42.12-146 -60201897-2018), obtained in tubular reactors in a stream of hot gases [RU 2219128, C01F 7/44, 20.12.2003]. It is allowed to use a similar product manufactured according to other technical specifications, but necessarily meeting the above requirements.

A weighed portion of the starting material is ground in a mill (ball, planetary, jet or any other) to agglomerates of particles with a volumetric average diameter of 5-25 microns. In some cases, PBTOG is used in its original state, i.e. without grinding, then the fractional composition of particle agglomerates is preserved.

A portion of PBTOG is hydrated with stirring for 2-4 h in weakly concentrated solutions of nitric acid heated to 50 ± 5 ° C (acid modulus not more than 0.1). Then the resulting suspension is filtered under vacuum and washed with either distilled water or technically prepared water that does not contain sodium. The result is a wet cake - cake.

Hydrothermal treatment of cake is carried out in an autoclave in aqueous solutions of nitric acid with the addition at the initial stage of a given amount of a lanthanum-containing source, mainly lanthanum nitrate, at a suspension temperature of 140-180 ° C for 6-16 hours. After the completion of hydrothermal treatment, the suspension is cooled to a predetermined temperature, but not higher than 90 ° C, the autoclave is unloaded, the contents of the vessel are repulped with distilled or technically prepared water to obtain a pseudoboehmite-containing suspension suitable for spray drying.

Next, drying is carried out on a spray dryer at an air temperature at the inlet to the dryer not higher than 350 ° C and continuous stirring of the repulped suspension. The finished powder of aluminum hydroxide is discharged from the receiving tank (glass) of the cyclone dust collector of the spray dryer.

The essence of the invention is illustrated by the following examples.

Example 1 according to the known solution [RU 2099135, B01J21 / 04, 20.12.97].

The raw material used is alumina powder with a specific surface area of 390 m ² / g, obtained by rapid dehydration of hydrargillite.

The alumina powder is ripened, that is, rehydrated by suspending the powder in water to a concentration of 250 g / l and keeping it for 24 hours at a temperature of 98 ° C, and at the beginning of the operation, an aqueous solution of lanthanum nitrate is added to the suspension in an amount corresponding to 5 % lanthanum, calculated as lanthanum oxide, based on the total weight of the stabilized final alumina. The pH is adjusted to 10 by adding ammonium hydroxide at the start of the operation.

After processing, a liquid / solid separation is carried out and the alumina is dried at 120 ° C for 12 h.

The aluminum hydroxide thus obtained is calcined for four hours at 1200 ° C in an ambient atmosphere, the finished product has a specific surface area of 52 m ² / g. After calcining at 1200 ° C for 24 hours in an ambient atmosphere, its specific surface area is 28 m ² / g.

The characteristics of the oxygen-containing compound according to example 1 are shown in the table.

Examples 2-7 illustrate the proposed technical solution.

Example 2

Aluminum hydroxide is prepared as follows. Take 150 g of a powdery product of rapid heat treatment of hydrargillite (PBTOG), ground in a ball mill to agglomerates of particles with an average volumetric diameter of 5-25 microns. Next, the crushed powder is hydrated with continuous stirring in a weakly concentrated (0.3 wt%) solution of nitric acid at a temperature of 50 ± 5 ° C for 2 hours.

Then the suspension is filtered under vacuum using a Buchner funnel and a Bunsen flask through a Blue Ribbon filter paper and washed with distilled water to a residual sodium content of 0.04 wt. %. The result is a wet cake - cake.

The cake is loaded into an autoclave, to which a 1.5% solution of nitric acid is added until the pH of the suspension reaches 1.0-2.0.

A solution of lanthanum nitrate (TU 2013-036-469133-78-2019) in an amount of 25 g is added to the suspension with stirring. The autoclave vessel is heated to 180 ° C and kept for 16 hours. Then the autoclave vessel is cooled to room temperature.

A suspension of aluminum hydroxide is discharged and dried in a spray dryer at a coolant temperature at the inlet to the separator of 220-350 ° C.

As a result, aluminum hydroxide is obtained containing isolated lanthanum atoms with a size of about 0.1 nm on its surface, with a surface density of 45-50 lanthanum atoms per 10 nm ² and a ratio of Al atoms to La atoms equal to 50. The value of n in the formula Al ₂ O ₃ ⋅nH ₂ O is 1.5.

The volumetric average diameter of the agglomerates of particles of aluminum hydroxide D according to example 2 is 5 μm.

The rest of the characteristics of aluminum hydroxide are shown in the table.

Example 3

Similar to example 2, only the hydration of PBTOG powder is carried out for 4 hours, and filtration is carried out with technically prepared water to a residual Na content of 0.001 wt. %. After that, a solution of lanthanum nitrate in an amount of 12.5 g is added to the suspension in the autoclave vessel, and the vessel is heated to 140 ° C and incubated for 6 hours.

As a result, aluminum hydroxide is obtained, additionally containing isolated lanthanum atoms with a size of about 0.1 nm on its surface, with a surface density of 25-30 lanthanum atoms per 10 nm ² and a ratio of Al atoms to La atoms equal to 100. The value of n in the formula Al ₂ O ₃ ⋅nH ₂ O is 1.6.

The volumetric average diameter of the agglomerates of particles of aluminum hydroxide D according to example 3 is 25 μm.

The rest of the characteristics of aluminum hydroxide are shown in the table.

Example 4

Similar to example 2, only a solution of lanthanum nitrate in the amount of 6.3 g is added to the suspension in the autoclave vessel in the amount of 6.3 g, while the autoclave vessel is kept at a temperature of 140 ° C for 16 hours.

As a result, aluminum hydroxide is obtained, additionally containing isolated lanthanum atoms with a size of about 0.1 nm on its surface, with a surface density of 12-15 lanthanum atoms per 10 nm ² and a ratio of Al atoms to La atoms equal to 200. The value of n in the formula Al ₂ O ₃ ⋅nH ₂ O is 1.9.

The volumetric average diameter of the agglomerates of particles of aluminum hydroxide D according to example 4 is 50 μm.

The rest of the characteristics of aluminum hydroxide are shown in the table.

Example 5

Similar to example 4, only a solution of lanthanum nitrate in an amount of 3.1 g is added to the suspension in the autoclave vessel, while the finished suspension of aluminum hydroxide after hydrothermal treatment is cooled to 90 ° C.

As a result, aluminum hydroxide is obtained, additionally containing isolated lanthanum atoms with a size of about 0.1 nm on its surface, with a surface density of 8-10 lanthanum atoms per 10 nm ² and a ratio of Al atoms to La atoms equal to 400. The value of n in the formula Al ₂ O ₃ ⋅nH ₂ O is 1.8.

The volumetric average diameter of the agglomerates of particles of aluminum hydroxide D according to example 5 is 100 μm.

The rest of the characteristics of aluminum hydroxide are shown in the table.

Example 6

Similar to example 4, only to the suspension in the vessel of the autoclave add lanthanum nitrate 6-aqueous in the form of crystalline hydrate in the amount of 0.45 g in terms of anhydrous lanthanum nitrate.

As a result, aluminum hydroxide is obtained, additionally containing on its surface isolated lanthanum atoms with a size of about 0.1 nm, with a surface density of 6-7 lanthanum atoms per 10 nm ² and a ratio of Al atoms to La atoms equal to 1000. The value of n in the formula Al ₂ O ₃ ⋅nH ₂ O is 1.8.

The volumetric average diameter of the agglomerates of particles of aluminum hydroxide D according to example 6 is 75 μm.

The rest of the characteristics of aluminum hydroxide are shown in the table.

Example 7

Similar to example 6, only to the suspension in the vessel of the autoclave add lanthanum nitrate 6-aqueous in the form of crystalline hydrate in the amount of 0.05 g in terms of anhydrous lanthanum nitrate.

As a result, aluminum hydroxide is obtained, additionally containing isolated lanthanum atoms with a size of about 0.1 nm on its surface, with a surface density of 5 lanthanum atoms per 10 nm ² and a ratio of Al atoms to La atoms equal to 10000. The value of n in the formula Al ₂ O ₃ ⋅nH ₂ O is 1.8.

The volumetric average diameter of the agglomerates of particles of aluminum hydroxide D according to example 7 is 40 μm.

The rest of the characteristics of aluminum hydroxide are shown in the table.

Thus, as can be seen from examples 2-7, the proposed method makes it possible to obtain aluminum hydroxide containing isolated lanthanum atoms on its surface, which opens up wide opportunities for obtaining effective and promising adsorbents, supports and catalysts based on it.

Table - Characteristics of aluminum hydroxides by examples example The ratio of Al atoms to La atoms Surface density of La atoms per 10 nm ² surface, atoms Phase composition of Al ₂ O ₃ ⋅nH ₂ O, wt. % Na, wt. % _{Textural characteristics of Al 2} O ₃ ⋅nH ₂ O calcined at 550 ° C pseudoboehmite χ-like phase Al ₂ O ₃ S _beats , m ² / g D, nm V, cm ³ / g one Isolated La atoms are absent These phases are missing 0.2 28 twenty 0.1 2 50 45-50 60 40 0.04 200 15.0 0.75 3 one hundred 25-30 75 25 0.001 244 9.4 0.45 4 200 12-15 80 twenty 0.04 252 9.2 0.60 5 400 8-10 85 15 0.04 252 9.1 0.59 6 1000 6-7 90 10 0.04 237 9.6 0.58 7 10000 5 95 5 0.04 300 8.0 0.57

Claims (7)

1. A method of preparing aluminum hydroxide containing isolated lanthanum atoms, characterized in that first the product of rapid heat treatment of hydrargillite is ground to particles with a volumetric average diameter of 5-25 microns, then hydrated in a 0.3 wt.% Solution of nitric acid, filtered and washed from impurity sodium, then wet sediment is subjected to hydrothermal treatment in the form of a suspension in an aqueous solution of nitric acid and a source of lanthanum, and after drying, aluminum hydroxide is obtained with the general formula Al₂O₃⋅nH₂O, where n = 1.5-1.9, consisting of pseudoboehmite and a disordered χ-like phase of aluminum oxide at a ratio of these phases, wt%: 60-95 pseudoboehmite, 5-40 disordered χ-like phase of aluminum oxide; containing isolated La atoms on its surface with a surface density of 2-50 atoms per 10 nm² surface and the ratio of Al atoms to La atoms equal to 50-10000; including constitutional water containing impurity Na in the range of 0.001-0.04 wt.%; specific surface area after calcining at 550 ° C is 200-300 m²/ g, average pore diameter - 8-15 nm, pore volume - 0.45-0.75 cm³/G. 2. The method according to claim 1, characterized in that as the initial product of rapid heat treatment of hydrargillite, a product with the following characteristics, wt% is used: hydrargillite not more than 3, boehmite not more than 10, disordered χ-like Al ₂ O ₃ , also called X-ray amorphous or amorphous phase, or ρ-Al ₂ O ₃ not less than 87; the proportion of weight loss during calcination at 800 ° C is within 6-10, the proportion of sodium oxide is not more than 0.3, the specific surface area is not less than 200 m ² / g. 3. A method according to claim 1, characterized in that lanthanum nitrate is used as a source of lanthanum in the form of crystalline hydrate or in the form of a solution. 4. The method according to claim 1, characterized in that the hydrothermal treatment of the wet sludge is carried out in an autoclave in aqueous solutions of nitric acid with the addition of a predetermined amount of a lanthanum-containing source at the initial stage, at a suspension temperature of 140-180 ° C for 6-16 hours. 5. A method according to claim 1, characterized in that the aluminum hydroxide suspension is dried in a spray dryer at a heat carrier gas temperature of 220-350 ° C. 6. The method according to claim 1, characterized in that the obtained aluminum hydroxide contains constitutional water in an amount of 22-25 wt.%. 7. The method according to claim. 1, characterized in that the obtained aluminum hydroxide is an agglomerate of particles with a volumetric average diameter of 5 to 100 microns.