DD215520A1 - METHOD FOR PRODUCING ALUMINUM OXIDE HYDRATES - Google Patents

Abstract

The invention relates to a process for the preparation of alumina hydrates. The object of the invention is a process for the preparation of alumina hydrates having a Na 2 O content of less than 0.01 mass%, d. are suitable as a component for the production of high-performance catalysts. The task consists in the development of a technologically simple process by which high-purity products are produced at low economic expenditure. According to the invention, the precipitate of aluminum salt solution containing 50 to 150 g Al deep 2O deep 3 / l and Alkalialuminatloesung with a content of 200 to 400 g Al deep 2O deep 3, if necessary with inflow of water u./o. Water glass solution and at a ratio of total volume flow rate per hour to volume of Faellgefaesses of not more than 10: 1 carried out, wherein the solids content of the suspension in Faellbehaelter 40 to 60 g Al deep 2O deep 3 / l entraegt and that after filtration of the Faellsuspension, during and / or after washing, steam is passed through the filter cake. The alumina hydrates can be used as catalyst components.

Description

VEB Leuna-Werke Leuna, the

"Walter Ulbricht"

LP 8261

Title of the invention

Process for the preparation of alumina hydrates

Field of application of the invention

The invention relates to a process for the preparation of alumina hydrates which can be used as catalyst components.

Characteristic of the known technical solutions

It is known that aluminum oxide hydrates can be prepared by precipitation from aluminum salt solution or aluminate solution with ammonia water, alkali solutions, mineral acids or aluminum salt solutions. By suitable choice of reactants, precipitation temperature, pH or other factors, different crystalline forms can be used, such as bayerite, boehmite or nordstrandite or the like Mixtures or amorphous products are produced · The resulting alumina hydrates contain impurities whose contents are mainly dependent on the proportion of impurities in the precipitating components · To produce products of high purity, such as

For high performance catalysts are required to produce, one endeavors to use starting materials which are largely free of interfering impurities, z, B · Ha ₂ O or Pe ₂ Oo. For this reason, one chooses as precipitating components in many cases, an aluminum salt solution and ammonia water, in which the concentration of interfering impurities can be kept low.

Methods are known (eg. B · DD-PS 138 459), are where obtained by mixing aluminum salt solution and ammonia water Äluminiumoxidhydrate which are suitable as a component for _t preparation of high-performance catalysts · In derartigan procedures ^ fall per ton algo more than 4 Tons of Sal-z, whereby the economy is adversely affected by a high cost of acid and ammonia and by high costs of wastewater treatment.

In DE-OS 2,125,625 a process for the preparation of alumina with pseudoboehmitartiger structure and low lapO content t by cases of alkali aluminate and nitric acid is described · This method is associated with a relatively high salt content and accordingly also has the above-mentioned wax parts · Further, in this process, re-mashing of the already-washed filter cake and subsequent washing with ammonia water and then with deionized water are necessary as additional technological steps to achieve Ha.sub.2 O contents of <0.01 mass%, as used for high-performance catalysts. B · for the catalytic reforming, the aim is to achieve

It is also known to produce aluminum oxide hydrates by precipitation from aluminate solution and aluminum salt solution. Although the specific salt attack is relatively low in this extremely economical process, high purification requirements also require a high washing effort.

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It is also known (DE-AS 1 542 386) that with increasing boehmite content of the alumina hydrates used, their deformability is improved and the mechanical strength of catalyst supports made therefrom is increased.

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Object of the invention

The aim of the invention is a method for producing high purity alumina hydra te with a Na ₂ 0 content of less than 0.01 Ma ^, which are also characterized by good ductility and high mechanical strength and can be used as a component of high-performance catalysts.

Explanation of the essence of the invention

The object of the invention is the development of a technologically simple process for the production of high purity alumina hydrates, which produces high purity products at low economic cost · This object is achieved by continuous precipitation of alkali aluminates and aluminum salt solution with vigorous stirring, at pH values between 6 and 9 and temperatures of 323 to 363 K dissolved by the precipitation of aluminum salt solution containing 50 to 150 g AlpO ^ / 1 and alkali aluminate solution containing 200 to 400 g AigOo / l »optionally with inflow of water and / or water glass solution and at a ratio of total volume flow rate per hour to volume of the precipitation vessel of not more than 10 t T is carried out, wherein the solids content of the suspension in the precipitation vessel 40 to bO g AloOo / l and that after filtration of the precipitation suspension during and / or after washing the filter cake steam is passed · Advantageously, saturated steam at a temperature of 373 to 393 K is used.

It is favorable if the boehmite content of the dried precipitate after passing the steam is at least 80 % .

Passing the steam through the filter cake is preferably before at a salt concentration of the mother liquor

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It is advantageous if the precipitate undergoes 1.5 to 3 hours at a maximum temperature of 343 K before filtration.

The production of the Aiuminiumoxidhydrate takes place primarily from aluminum nitrate solution and Hatriumaluminatlösung. Bs is favorable if, by addition of waterglass solution into the precipitation vessel, the SiO.sub.2 content of the Aiuminiumoxidhydrate is up to 5 Ma ^. Advantageously, 0.2 to 1.5 kg Sattdam-pf per kg AIpOo prevailed »

In the solution of the problem shows that it is also possible Aiuminiumoxidhydrate with SiO 2 contents up to 5 Ma% with equal success, by precipitation of aluminum salt solution and Alkalialuminatlösung with the addition of water glass to produce.

The drying of the precipitate is then carried out at temperatures of 363 to 423 K. Surprisingly, the produced by this simple technology Aluminiumoxidhydrat-e products produced by ammonia precipitation are at least equivalent in purity and superior in terms of their suitability as a catalyst component. This manifests itself in particular during the deformation of , milled products and the strength of the blanks ·

embodiment

example 1

According to the invention, 600 l of aluminum nitrate solution, containing 100 g of Al 2 O / l, of sodium aluminate solution with an AloOv content of 300 g / l and 3 m of water are continuously added with stirring to the 500 l of precipitation tank and at a pH of 7.5 ", the AlgOv

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Content of the precipitation suspension 50 g / l and the sodium nitrate content is about 70 g / l. The temperature in the precipitation vessel is kept at 343 K. The precipitate then passes into a stirred tank from where it is filtered without further addition of water to the suspension, after a mean residence time of 2 hours and washed with about 20 wr water per ton of Al ₃ O ₃ , After this wash, which takes about 10 minutes, the Na ⁺ concentration of the mother liquor in the filter cake is 8. 1 × ³ × 1 × Then, per ton of Al ₃ O ₃ > 1000 kg of salt cake at a temperature of 378 K, the mixture is passed through the filter cake within 20 minutes, then washed again with 20 ml of water per ton of AIgOo and the filter cake, the 30 Including% Al ₂ O ₃ , dried at 383 to 423 K. The content of the boehmite content of the dried product is 90 mass%.

Example 2 (comparison)

A product prepared and filtered under the same conditions as in example 1 is filtered after filtration with about 100 nr of water per ton of Al ₂ O _{3 for} 2 hours and the filter cake containing 30 mass% of Al ₃ O ₃ at 383 to 423 K dried.

Example 3 (comparison)

600 l of aluminum nitrate solution containing 100 g of AlpOo / 1, sodium aluminate solution having an Al ₂ O ₃ content of about 300 g / l and 1 m of water are continuously fed with stirring to the precipitation vessel and at a pH of • 7, 5 precipitated, wherein the content of Al ₃ O ₃ 'in the precipitation suspension 100 g / l and sodium nitrate is about 140 g / l · The temperature in the precipitation vessel is maintained at 343 K. · The precipitation suspension passes into a stirred tank, in which per hour

3 3 m of water are metered, then filtered after a mean residence time of 2 hours, washed with about 100 m "water per ton of Al ₃ O ₃ 2 hours and the filter cake containing 30% by mass of Al ₃ O ₃ at 383 bis 423 K dried

Example 4 (comparison)

Under the same conditions as in Example 3 produced product is treated after filtration in the same manner as in Example T ·

Example 5 (comparison)

900 1 aluminum nitrate solution containing 100 g AlJnk / l per hour, ammonia water of a concentration of about 25 % and 1 m of water to the Pa11behälter continuously fed and precipitated at a pH of 7.6. The AlgO, concentration in the precipitation suspension is 30 g / l and the content of ammonium nitrate 145 g / l · The precipitation suspension is then treated in the same manner as in Example 3.

Example 6

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Were ErfindungsgemäJfä per hour 600 1 Aluminiuranitratlösung containing 75 g Al ₃ O _3, and 20 g SiOg / l, Natriumalumina tlösung with an Al _o 0v * content of 300 g / 1 and 3 Kr water to the precipitation tank continuously fed with stirring and at a The precipitate precipitation is 45 g / l and the sodium nitrate content is 65 g / l. The temperature in the precipitation vessel is kept at 343 K. The precipitate is then treated in the same way as in Example 1 further treated. The SiO 2 content of the aluminum oxide hydrates produced in this way is 5% by mass, based on AlpOo. The boehmite content of the dried product is 90 MaS. - ·.

3Ρ · Ma% • Na ₂ O Surface mr / g Particle size 10- ¹ V Boehmite % Salt case t / t Al ₂ O ₃ 1 ^ 0.01 330 33 90 1.4 2 0.04 260 30 65 -: 70 ¹ > 4 3 0.06 280 35 70 1.4 4 0,035 290 37 80 1.4 i '  , 5 <CO, 01 300 32 80. 4.8: υ ^ 0,01 310 33 90 1,4;

As a comparison of the results shown in the table shows, the processing goal is only achieved by combining the actions according to the invention (Examples 1 and 6). The alumina hydrates prepared according to the invention are distinguished, in particular, by high purity, strength and good formability.

Claims (3)

Invention claim. A process for the preparation of alumina hydrate from alkali alumina solution and aluminum saline by continuous precipitation with vigorous stirring at pH's between 6 and 9 and temperatures of 323 to 363 K, characterized in that the precipitation from aluminum salt solution with a GelSite of 50'bis 150 g Al-O ^ / l and Alkaliaiuminatlösung with a content of 200 to 400 g AlgO ^ / l, optionally with inflow of water and / or Yiasserglaslösung and at a ratio of Gesamtvoiumendurchsata per hour to volume of the precipitator of a maximum of 10: 1 carried out is, wherein the solids content of the suspension in the precipitation vessel 40 to 60 g AlpÖ ^ / l, and that after the filtration of the precipitation suspension, during and / or after the washing, steam is passed through the filter cake · 2. The method according to item 1, characterized in that saturated steam at a temperature of 373 to 393 Kverwendet. Method according to items 1 and 2, characterized in that the boehmite content of the dried precipitate after passing the vapor is at least 80 % . 4 · Method according to item 1 to 3, characterized in that a passage of the steam through the filter cake at For salt concentrating the courage te:
8 · 10 "" ^ m ^ ol / l is made. -2 of a salt concentrate of the mother liquor from 10 to The process according to items 1 to 4 is characterized in that the precipitate ages for 1.5 to 3 hours at a maximum of 343 K before filtration. G. The method according to item 1 to 5, characterized in that the preparation of the alumina hydrates of Aluminiumhitratlösung and sodium aluminate solution. 7 · Method according to items 1 to 6, characterized in that the SiO 2 content of the alumina hydrates is up to 5% by the addition of water glass solution in the digestion vessel; 8. The method according to item 1 to 7, characterized in that 0.2 to 1.5 kg of saturated steam per kg AlpOo be enforced.