DE2725496B2 - Process for the preparation of sodium zeolite A. - Google Patents

Description

15th

This invention relates to the subject matter characterized in the claim.

The properties, formulas and preparation of zeolite A are already known and, for example, in the U.S. Patents 3,114,603 and 3,119,659.

According to the process of US-PS 31 14 603 synthetic zeolite A is obtained in a two-stage process, in which the reactants are brought together and in a first stage at a temperature of 20 ° to Digested at 55 ° C for at least 2 hours and then in a second stage at at least 75 ° C be heated for a long time. Generally one needs for both steps in the examples of the US-PS 3114 603 a preferred total time of 7.5 to 48 hours. Those in the procedure outlined above The necessary reaction times are very inconvenient for a technical implementation, as this requires the system to be designed very large, which in turn increases the product costs. on the other hand it is often troublesome to carry out the process in two stages, but this was necessary to achieve a product of high purity (with over 80% of zeolite A) according to the state of the art is required for the formation of By-products or impurities, such as. B. other zeolites, hydroxysodalite or amorphous substances, to avoid or reduce.

The invention was based on the object of providing a one-step process for the production of zeolite A. create that can be carried out in a shorter time and delivers a product of particularly high purity.

This object was achieved according to the invention by the method outlined in the claim.

The zeolite A has the formula

1.0 ± 0.2 Na ₂ O: Al ₂ O ₃ : 2.0 ± 0.5 SiO ₂ : YH ₂ O,

wherein Y can have a value up to about 5.1.

A preferred zeolite is described in BE-PS 814 874 by the formula

Na ₁₂ (AlO ₂ · SiO ₂ ) ₁₂ · * H ₂ O

where χ is a number from 20 to 30, and preferably about 27. The preparation of such zeolites is desired by the process of the present invention.

According to the invention, it is possible to obtain the zeolite A with a purity of 90% or higher. So it was found that, for example, a reaction time of 2 hours at 85 ° C is sufficient to achieve an im μ substantially complete conversion to a final product with a purity of 95% or above reach.

It is particularly advantageous to work according to the invention when the molar ratio H ₂ O / Na ₂ O is about 25 to 50, and in particular 40

The product obtained by the process of the present invention is easily filtered or centrifuged recovered, after which it is washed to remove mother liquor and impurities. The washed Product is then dried to remove residual water content.

Although the mother liquor removed from the product and the wash water are completely or partially under Addition of fresh reactants can be recycled into the reaction stage, will However, this is generally not preferred, but they are used for the recovery of what is still contained therein Product subjected to one or more additional crystallizations. More preferred in one such In the process, an aqueous solution of NaOH is obtained, which is more successful with metakaolin converts as an aqueous NaOH solution that is still in the Contains circular mother liquor

Of course, the inventive method includes the cycle of the mother liquor and the Do not use detergents, and under suitable conditions such a cycle can also be advantageous be. However, in order to avoid an accumulation of impurities, the entire mother liquor, the purification of part of the circulated stream is desirable or necessary.

The present invention uses the meta form of amorphous kaolin called metakaolin or the equivalent product, which is preferably obtained by firing kaolin at a temperature of about Maintains 550 ° to about 900 ° C. Such burning is known to the person skilled in the art and is, for example, in US Pat US Pat. No. 3,114,603. As can be seen from this US patent, it is common desirable a longer period between the firing of the kaolin and its use in the to avoid existing proceedings.

The following examples show preferred embodiments of the present invention.

example 1

A 1 liter round-bottomed flask equipped with a heating jacket and stirrer is filled with 250 g of H ₂ O at room temperature, then 34.5 g of NaOH beads are added and the mixture is stirred until the NaOH has dissolved. 40 g of metakaolin are added and the mixture is heated to 85 ° C. and the flask and contents are kept at this temperature for 2 hours with a stirrer.

Remove the heating mantle and filter the contents of the flask to collect the solid product a Buchner funnel, wash the product with 500 g of water and dry it in the oven for 5 hours or more at 100 ° C.

By X-ray diffraction analysis of a product sample, it was found that a zeolite A with 95% strength odei higher purity (ASTM X-ray powder diffraction pattern "File Card No. 11-590").

In this example the following molar ratios are used:

Na ₂ O / Al ₂ O ₃ = 2 SiO ₂ / Al ₂ O ₃ = 2 H ₂ O / A1 ₂ O ₃ = 78 H ₂ O / Na ₂ O = 39

Tabel

Example H ₂ O
(G)

NaOH

(G)

Metakaolin

(G)

Temperature time

Γ C) (min.)

Product (%)

Zeolite A Zeolite C Phillipsite

1 250 34.5 40 85 120 95 - - 2 125 34.5 40 80 120 95 - A. 250 34.5 40 90 120 63 4th 250 34.5 40 85 150 96 0 - 5 250 34.5 40 85 220 103 0 B. 250 34.5 40 90 120 78 0 Some C. 250 34.5 40 90 180 76 0 Some D. 250 34.5 40 90 240 71 0 0 E. 250 34.5 40 85-86 60 Amorphous material 6th 250 34.5 40 85-86 120 96 0 _ 7th 250 34.5 40 85-86 180 94 0 - 8th 250 34.5 40 85-86 240 93 0 9 250 34.5 40 85 150 113 0 _ F. 160 34.5 40 90 65 54 11th - G 160 34.5 40 90 120 52 13th - H 160 34.5 40 90 150 50 12th - 1 160 34.5 40 85 63 60 11th _ 10 160 34.5 40 85 123 62 11th _ 11th 160 34.5 40 85 183 60 14th - 12th 160 34.5 40 80 120 104 0 - 13th 160 34.5 40 80 185 104 0

Example 2

Repeating the Example 1 using 125 g of water instead of 250 g and a temperature of 80 ⁰ C instead of 85 ° C. Similar results are obtained. The H ₂ 0 / Na ₂ 0 ratio is 20.

Example 3

579 liters of deionized water are placed in a 946 liter reactor equipped with a steam jacket and stirrer. 83 kg of sodium hydroxide beads are then added to the reactor. The mixture is heated to 81.6 ° C. and stirred until the beads have dissolved. Then 92.5 kg of metakaolin are added and the temperature is increased to 85 ^° C.

This temperature is kept for 2½ hours with stirring upright The reaction mass is cooled to about room temperature and leads to the removal of supernatant mother liquor in four batches to a centrifuge. The centrifuge cake is washed with it 992 liters of deionized water. 130 kg of zeolite A are obtained. The product is according to X-ray diffraction analysis essentially 100% zeolite A.

Examples 4 to 13
and Comparative Examples A to I.

Example 1 is repeated in experiments under varying conditions. The results are in the Table given together with the results of Examples 1 and 2.

Claims (1)

Claim: Process for the production of sodium zeolite A by converting metakaolin and NaOH into aqueous solution with stirring at elevated temperatures, filtering off, washing and drying of the zeolite obtained, characterized in that the reaction with a Molar ratio H2O / Na2O from 15 to 100 in one Performs one-step process at a temperature of 80 ° to 85 ° C for 2 to 4 hours