DD148625A1 - PROCESS FOR THE SYNTHETIC PREPARATION OF CRYSTALLINES, PARTIAL CRYSTALLINES OR AMORPHOUS ALUMOSILICATES - Google Patents

Abstract

The invention relates to a process for the preparation of crystalline, semi-crystalline or amorphous aluminosilicates which can be used as adsorbent, ion exchanger, catalyst and catalyst carrier. According to the invention, the starting materials and intermediates of the aluminosilicates are intensively agitated with inert milling bodies, partly or throughout the required reaction time.

Description

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Process for the synthetic preparation of crystalline , semi-crystalline or amorphous aluminosilicates

Field of application of the invention:

The invention relates to a process for the synthetic preparation of crystalline, semi-crystalline or amorphous aluminosilicates which can be used as adsorbent, ion exchanger, catalyst and catalyst support.

Characteristic of the known technical solutions:

Crystalline, semi-crystalline and amorphous aluminosilicates of the general formula Na _x (AlO ₂ ) (SiO ₂ ) _z in the anhydrous state, in which x, y and ζ represent numbers from 2 to 15, can be prepared from various starting materials. Essentially, a hydrogel is first prepared from a source of SiO ₂ and Al ₂ O ₃ , which is then subjected to controlled aging and, in the case of the crystalline and semicrystalline products, to controlled crystallization. The known procedure for the production of crystalline, partially crystalline and amorphous aluminosilicates is characterized by the steps:

a) Preparation of the starting materials (eg dissolution of Al ₂ O ₅ in NaOH, preparation of the sodium silicate solution, activation of clays or other natural raw materials)

b) mixture of the starting materials according to the desired aluminosilicate type to a »sodium aluminosilicate gel

0) aging of this produced aluminosilicate gel

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d) crystallization of the aluminosilicate gel β) separation of the desired aluminosilicate and its further processing

The technological conditions and the apparatuses used are known for discontinuous and continuous preparations and described in numerous publications and patents (DOS 2832947, US 2635304, DWP 138304, DWP 132069, DWP 138968, Breok, DW "Zeolite Molecular Sieves", Grubner, 0. "molecular sieves").

The most common reaction apparatus for steps a) to d) is a reaction vessel with stirring device, wherein a different stirring intensity in the individual stages is present.

For continuous processes also reactors with stirrers are proposed. A Naohteil the reactors with stirring, auoh such with intense stirring, e.g. Turbine stirrers, are the formation of deposits and crustations on the vessel surfaces and surfaces of the stirring devices. For the purposes of process engineering, such deposits are sites of stationarity and lead to the inhomogeneity of the reaction conditions. They are therefore a disruptive factor for the flow behavior of the reaction mixture. In the synthesis of the crystalline, semi-crystalline and amorphous aluminosilicates these deposits and Krustatiouen crystal nuclei for foreign phases. The synthesis of the aluminosilicate then runs uncontrollably from and leads to poor quality products or entirely to undesirable products. In addition, the disturbance of the heat transfer locally changes the synthesis conditions. It is known that the Temperaturkonstanz in the synthesis, especially of crystalline products, is of great importance.

Another disadvantage of the known Alumosilikatsyntb.esen lies in the long production times. Synthesis time shortening may be e.g. achieved by increasing the reaction temperature or the alkali content of Ansätzmisohung

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In both cases, however, the formation of other undesirable phases is promoted. A: Increasing the alkali content are already duroh the "known synthesis fields limits.

Object of the invention:

The aim of the invention is a process for the synthetic preparation of crystalline, partially crystalline or amorphous aluminosilicates with reduced production times and consistent quality of the products.

Explanation of the essence of the invention:

The invention has for its object to find a method for the preparation of crystalline, partially crystalline or amorphous aluminosilicates, which prevents the occurrence of deposits and rusting. According to the invention, the starting materials or intermediates of the aluminosilicate synthesis are intensively agitated with grinding media of an inert material in at least one of the preparation stages of mixing, aging and crystallization, or in all three production stages. Grinding media in this sense are e.g. Balls made of materials inert to the chemical reaction conditions. These include steel, metals or alloys, porcelain or ceramic materials. The grinding media may also be of ellipsoidal, angular or other shape. For example, in the case of spherical particles, the grinding media should have a diameter of 0.5 to 50 mm, taking into account the dimensions of the reactor and the type of stirring device. The amount of inert grinding media added should correspond to 1 to 50 vol.%, Preferably 3 to 15 vol.%, Of the reactor contents (volume of the synthesis mixture + volume of the grinding media). In any case, sufficient action must be ensured. The implementation of the invention is just as possible in batch mode as in continuous flow mode.

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It has been found that the influence of the inert media is not limited to the suppression of the foreign phases alone. The frictional, bouncing and repulsive force of the agitated grinding media also results in the formation of a very homogeneous suspension of aluminosilicate intermediates in which increased nucleation and agglomeration occur accelerated crystallization of Alümosilikate expires. Furthermore, finely divided products are formed under the influence of the inert agitated grinding media, since the formation of agglomerates is prevented. Other performance characteristics, such as redistribution and ion exchange, are also favorably affected.

According to the invention, the alumino-silicates can be prepared by stirring the starting materials in a stirred tank with an appropriate amount of grinding media, eg _e balls, wherein the reaction parameters such as temperature and the composition of the starting materials must be adapted to the corresponding desired aluminosilicate type. As starting materials are known, for example, sodium aluminate, sodium silicate, silica sol, Al ₅ O, and / or SiO ₉ -containing solid products, such as metakaolin and alkali. Furthermore, any apparatus is suitable in which grinding media can be moved under synthesis conditions (eg tubular drum mills, ball mills), Mahlkör permenge, type and size depend on the type of reactor in a known manner.

The following are the embodiments by way of examples are explained, but without the execution of the invention should be bound to the apparatus used or carrying out the experiments

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EXAMPLES example 1

In a continuously operated stirred tank made of V2A steel, a dilute sodium aluminate and sodium silicate solution in separate streams at a temperature of 20 ⁰ C are metered so that the concentration ratios in the reactor 2.1 Na ₂ O: Al ₂ O ₃ : 1.7 SiO _2:... amount to 52 H ₂ O The mean residence time is 40 min * The reaction temperature in the stirred vessel is adjusted to 90 ⁰ C. The mixing is performed by a Euhrer with 225 U / min The aluminosilicate obtained in steady state by filtration and washing, contains 80 mass- # zeolite 4A, wherein by X-ray analysis, a content of above 5 mass # hydroxysodalite is determined.

Example 2

The procedure is essentially analogous to Example The synthesis mixture 15 vol .- # steel balls, based on the reactor contents (volume of the synthesis mixture + volume of the balls) was added. The diameter of the balls is 10 mm. At a synthesis temperature of 90 ⁰ C, a Dxehzahl the stirrer of 225 U / min, a mean residence time of 40 minutes and the above concentration ratios an alumino-silicate is obtained in the stationary state, which consists of 94 mass of Zeolite 4A. Traces of crystalline impurities are undetectable.

Example 3

In contrast to the first two examples, Examples 3 and 4 are carried out in discontinuous batch operation. A kaolin with a kaolinite content of 83 % is converted by heat treatment at 800 ⁰ C in metakaolin. Major oh 'addition of NaOH and water will be a suspension of the composition

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100 O ₂ O prepared AEIE after 5 minutes intensive mixing at room temperature "in the äiskontinuierlichen stirred tank transferred is within a further 5 minutes the suspension to the synthesis temperature of 90 ^0: 3 Na ^ O VAl ₂ O _3: 2.1 SiO _2. C. and stirred at a speed of 225 rpm The proportion of zeolite A as a function of the synthesis time is shown in Table 1.

Example 4

Analogously to Example 3, the synthesis mixture is prepared and stirred in a batch stirred tank in the presence of 10 vol .- # steel balls with a diameter of 10 mm at 225 U / min. The proportion of zeolite A as a function of the synthesis time is shown in Table 1.

Table 1: Content of zeolite 4A in Content of Ze 8th Dependence on the synthesis time without balls Example 3 31 O 56 olith 4A (Massel) Synthesis time min O 74 10 vol .- # balls, based on the reactor contents Example 4 20 O 82 0 30 84 2 40 40 50 72 60 80 70 83 80 84 90 84 100 84

The comparison of Examples 3 and 4 emphasizes the activating influence of the moving spheres on the preparation of aluminosilicates at shorter synthesis times.

Claims (4)

-7- 218504 • 4 Invention ideas 1. Verfahren- to synthetic production of crystalline, semi-crystalline or amorphous aluminosilicates, characterized in that in at least one of the stages of preparation mixing, aging or crystallization, or in all three of these production stages, the Auagangs- and intermediates of aluminosilicate synthesis with MahlkcJrpern from an inert material " to be moved. 2. Method according to point 1.,
Please note that the grinding media are balls. 3. The method according to item 1 and 2, characterized in that the proportion of the balls in the reactor contents of 1 to Vol .- #, preferably 2 to 15 vol.-flS is. 4. The method according to item 1 _O to 3, characterized in that the production takes place continuously.