DE1767906A1 - Process for the production of zeolites with a faujasite structure - Google Patents

Description

PAINT FACTORY BAYERAG 1767906

LEVIRKUSKN-Baycnmk Pateat AbbeyUua *

June 27 , 1968

Process for the production of zeolites with

Eaujasite structure

The invention relates to an improved process for the production of zeolites with a faujasite structure. The inventive method works in comparison to the known faujasite synthesis method with a significantly increased space-time yield.

Zeolites are generally understood to mean a group of crystalline, hydrated aluminosilicates or polyvalent bases that give off their water without changing the crystal structure and other compounds instead of the distant water, and which are still capable of base exchange.

The crystal structure of these aluminosilicates can be described as three-dimensional network of SiO, and AlCL tetrahedra describe, whereby the tetrahedra are represented by shared oxygen

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atoms are connected. Piping arrangement leads to an electrical charge excess of aluminum, which is balanced by the sitter In additionally installed cations mainly Alkall- and Erdalkallmetalle, · Accordingly can be given for all zeolites following general formula:

^Me 2 / n ° ^{: A1} 2 ° 3 ^{: x Si0} 2 ^{! y H} 2 °

Me means a metal of η or hydrogen; the values for χ are in the range from 1.8 to 10, those for y range from 0 to etv / a ö.

However, the specification of the chemical composition is not sufficient to characterize a certain zeolite, as a large number of different zeolite types are known, which are mainly characterized by their crystal structure differentiate. The lattice structure also essentially determines the properties of the zeolites, which are used for their technical application as specific adsorbents or as catalysts are decisive.

An important property of the zeolite structure is its formation of cavities of constant dimensions, which are connected to one another by regularly arranged channels. These cavities are generally occupied with water molecules. By removing this zeolite bound Water, the cavities become free to accommodate others

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Substances, whereby naturally only those molecules can enter the lattice whose dimensions are smaller than the openings to these cavities. Because of this property zeolites are referred to ⁿ as "molecular sieves, and according to their forums diameter in fine-pore (3-5 Å) and wsitporige (3-10 iii). Divided zeolites or molecular sieves to the wide pore zeolite is one of the relatively rare mineral faujasite, the synthetic Analogues can also be assigned the designations Z 14 Na, Z 14 HS, Zeolite X, Zeolite Y, Zeolite 13 X, Zeolite 10 X, etc.

A detailed analysis of the faujasite structure can be found in Bergerhoff et al., Min. (1958), p. 193. The cubic faujasite structure (Pd 3 m) allows a very wide variation in the SiOg / AlgOj ratio, which naturally affects the size of the lattice constant a ₀ . An increase in pp ^ within the possible limits from 2 to about 6 corresponds to a decrease in the lattice constant a from about 25.0 A to about 24 »6 £. Furthermore, the type and amount of exchangeable cations also cause changes in the lattice constants, without fundamentally changing the structure type. Since the quantitative relationships are also largely known for these shifts, the analyst does not have any difficulties in evaluating and assigning the X-ray diagrams to one and the same grid type, namely the faujasite structure, especially since variable SiOp / AlpO ^ ratios

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not only found in zeolites, but also in many other aluminum silicates.

The known methods for preparing synthetic zeolites of the faujasite included can be generally classified into two methods divide:

1. Tendon procedure

2. Precipitation process

depending on whether the gel used for crystallization is represented by a precipitation or a melt.

In the so-called melting process, SiO ₀ - and ΑΙ, -, Ο -, - containing

C-C-J

Starting materials possibly sintered or melted together with the addition of fluxes W and then brought to crystallization in water or dilute lye. For example, alumina-containing disodium borosilicate glasses can be converted into crystalline zeolites of the faujasite type by heating in water to 60-100 g.

In the so-called precipitation process _{, sodium aluminum silicate gels are precipitated from solutions of a SiC 2} and Al 2 0 component with the addition of sodium hydroxide solution, and these then under

~ the cutter liquor at an elevated temperature, preferably at

ο
100 0, brought to crystallization.

Both processes have the disadvantage that reproducible results can only be obtained if very specific conditions are observed and that crystallization must be carried out in very dilute solutions, since otherwise other and frequently technically undesirable aluminosilicates will be formed. The V / ater content mixtures suitable approach for the synthesis of faujasite is in general 90-98 XoI- ^. This

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The disadvantage is particularly serious since the crystallization of the zeolites with the faujasite structure takes place slowly and usually very long crystallization times, e.g. 48 hours, have to be used.

The method according to the invention overcomes this disadvantage nr] fl makes it possible to produce faujasite with a significantly higher volume yield.

It is characterized in that at room temperature aluminosilicate gels from reaction mixtures with a Composition, expressed by the molar ratios of the oxides, in the range of

)
₂₂ ) = 1 »5 to 2.0

H ₂ 0 / lia ₂ 0 = 30 to 50

fails, it is then separated from the mother liquor and brings at temperatures of 40 to 100 ⁰ G for crystallization.

When practicing the method according to the invention, a gel is first precipitated in a relatively dilute solution, preferably from sodium aluminate and sodium silicate solutions with the addition of ITaOH, and this is homogenized by stirring. Before the hydrothermal treatment, however, the gel is separated from the mother liquor, as a result of which the time-consuming crystallization step takes place in an approach that is considerably richer in solids. For this purpose, the separated, still moist, not washed gel is placed in a closed reaction vessel at an elevated temperature (40 to 100 ⁰ G)

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held. During the hydrothermal treatment, the initially solid gel liquefies again, i.e. it takes place Separation into a solid, crystalline and a liquid phase. This allows the reaction products to end Implementation can be well separated from the small amount of newly formed mother liquor. The crystalline product is washed out, dried and optionally activated.

The composition of the reaction mixture is critical to the production of a particular type of zeolite. For example, teaches German Patent 1,038,016 for the production of "Zeolite X", a Faujasite with a SiOp / AlpO ^ ratio of 2.5 + 0.5, that pure preparations are obtained only when the composition of the reaction mixture is expressed as molar ratios of the oxides, is within the following limits:

3i0 ₂ / Al ₂ 0 ₃ = 3 to 5 Na ₂ O / SiO ₂ = 1.2 to 1.5 H ₂ 0 / Na ₂ 0 = 35 to 60

In comparison to this, the process according to the invention manages with significantly lower SiO ₂ / Al ₂ O, ratios and thus lower amounts of SiIicate solutions in the gel precipitation.

The gels precipitated in the range according to the invention are excellent after a short homogenization (about 5 minutes) filterable, so that their separation from the mother liquor does not present any technical difficulties.

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For subsequent crystallization, it has proven to be advantageous to age the gels initially at about 4-O ⁰ C and only then be heated to crystallization temperature. However, even if higher temperatures are used immediately, technically valuable products are obtained which can be contaminated by a maximum of 5-10 Ji of other zeolites.

When carrying out the process according to the invention in the technical Haßstab it can be for reasons of Easier warning transition when heating up can be advantageous if you apply the solid gel before the hydrothermal treatment mixed with so much liquid, e.g. water or dilute iatron lye, that a stirrable suspension arises. The filtered gel is preferably dissolved in up to 6% by weight of sodium hydroxide solution in an amount that is at most 1/4 of the volume corresponds to the filtered mother liquor, suspended

The gel is preferably separated from the mother liquor 1 to 10 minutes after the precipitation. To optimal To achieve products, crystallization times of about 1 to 2 days are used. With a pre-treatment

ο of the gel at temperatures of around 25 - 40 C and one

Period of about 2 to 30 hours, the thermal

V Q

Treatment at elevated temperatures of 60 to 150 G, preferably 85 to 100 ⁰ C, can be limited to a period of 12 to 24 hours.

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The space yield of the method according to the invention is at least ' 2-3 times larger, its reproducibility is optimal.

The method according to the invention is explained in more detail below with the aid of examples:
Example 1:

To a mixture of 100 ml of sodium aluminate solution (density: 1.36; 3.4 mol Na ₂ O / lj 2.0 mol A1 ₂ O, / 1; = solution A) and 17.2 ml NaOK (density: 1.4 &; e, 3 mol ITa ₂ O /!) a solution of 69 * 2 ml water glass (density: 1.34; 1.7 mol Na ₂ O / l; 5.78 mol SiO ₂ A; = Solution S) in 260 ml H ₂ O was added. The concentrations of this mixture correspond to the following oxide ratios:

3i0 ₂ / Al ₂ 0 ₃ = 2.0

lia ₂ 0 / Si0 ₂ = 1.5

H ₂ 0 / Na ₂ 0 = 40

The gel is homogenized by briefly stirring and then immediately separated from the mother liquor. The filter cake, which has been sharply suctioned off but is still moist, is first ^{aged for 24 hours at 40 °} C. in a closed reaction vessel without being washed out beforehand. The temperature is then increased to 100 ⁰ O and crystallized at this temperature for 24 hours.

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The resulting crystal slurry is washed out to pH 9-10 of the draining water and then dried at about 100 ° C.
Result:

X-ray analysis: pure zeolite with paujasite

structure

Lattice constant a _Q = 24.982 X

Adsorption capacities at 25 0:

for H ₂ O (at 10 torr): 30.8 g / 100 g of anhydrous substance for η-butane (at 760 torr): 15.1 g / 100 g of anhydrous substance

Example 2:

To a mixture of 100 ml of solution A (see example 1) and 20.7 ml of ITaOH (density: 1.48) was very rapidly under a solution of 51.8 ml of the water glass (solution S) in 273 ml of HpO was added with vigorous stirring. The composition this reaction mixture corresponds to the following molar ratios of the oxides:

SiO ₂ Al ₂ O ₃ = 1.5

Na ₂ O / SiO ₂ «2.0

H ₂ 0 / Na ₂ 0 = 40

The precipitated gel was stirred for 5 minutes at room temperature and then separated from the mother liquor by filtration. The still moist filter cake, which had been sharply suctioned off, was immediately ^{brought to crystallization in a closed reaction vessel without previous aging at 85 °} C. in 48 hours. The resulting crystal was washed with distilled water to a pH of 9-10, and then dried at 100 ⁰ C.

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Result:

X-ray analysis: Faujaslt-type zeolite (contaminated

due to approx. 7 9b zeolite of the A-type)

Example 3:

To a mixture of 400 ml of solution A and 83 ml of sodium hydroxide solution, £ 08 ml of solution S in 1090 ml of H ₂ O were added at room temperature with vigorous stirring. After a short homogenization (approx. 3 minutes), the precipitated gel was separated from the mother liquor by filtration ^{brought to 100 °} C. over 2 hours with stirring and left for crystallization without stirring for 24 hours at 100 ^° C. The reaction product was filtered off, washed out and dried at about 100 ° C.

Result:

X-ray analysis: zeolite of the gaujasite type, lattice constant

24.984 α (impurities i.e. zeolite of the A-type)

Gaujasite type zeolite, lattice const a_ = 24.984 α (contaminated by approx. 7 # Zlith T)

Adsorption capacities at 25 ⁰ C:

for H ₂ O (at 10 Torr): 30.1 g / 100 g of anhydrous substance

for η-butane (at 760 Torr): 14 »5 g / 100 g of anhydrous substance

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Claims (4)

Pat entanstr ttche ^ 1. Process for the preparation of zeolites with a faujjasite structure by hydrothermal treatment of sodium aluminosilicate gels, characterized in that the gels at room temperature from reaction mixtures with a composition expressed in terms of the boiling ratios of oxides, in the range of: SiO ₂ Al ₂ O,) ^{ά ά} * = 1.5 to 2.0 Na ₂ 0 / Si0 ₂ ) K ₂ 0 / Na ₂ 0 >> 30 to precipitates, it is then separated from the mother liquor and crystallized ^{at temperatures of 40 ° to 10O 0 O.} 2. The method according to claim 1, characterized in that the QeIe 1 to 10 minutes after the F & iir.ng of the mother liquor separates. 3. The method according to claim 1 and 2, characterized in that the gels separated from the mother liquor are first ^{aged at a low temperature (25-4O 0} C) and only then crystallizes at a higher temperature (85-10O ⁰ C). IeAH ₅₈₅ -11- ¹⁰⁹ 8 «6 / <KS9 BATH ORIGINAL 4. The method according to claim 1 to 3, characterized in that the separated from the mother liquor QeIe with water or dilute sodium hydroxide solution up to a maximum of 6 wt .-% in an amount of a maximum of 1/4 the volume of the filtered mother liquor is mixed to form a stirrable suspension. 109886 / (H 59 - 12 - BATH ORIGINAL