DE2560437C3 - Process for producing a crystalline zeolite powder of type A - Google Patents

Description

fraction Portion Around) (Ge\v%) < 5 25-35 <10 90-93 <15 91-97 <20 93-98

1.0 ± 0.2 Na,0 : A1,O _; : 1.85 ± 0.5 SiO _: · y H ₃ O,

where y is a value up to 6, with at least 99.5% by weight of particles below 30 µm in diameter and with at least 90% by weight of particles below 10 µm and with 50% by weight of particles below 6.5 µm at most and with a particle spectrum

fraction Portion t .-.ml iGow.A.) "^. 5 25-35 <l() ^1K ) -93 <15 ¹ Jl-97 <20 ^l )3-98

10

15

20

by hydrothermal crystallization of a sodium aluminate/water/silicate synthesis mixture containing SiO ₂ , AlO ₃ , Na ₂ O and water, with an optionally connected tempering stage, characterized in that an aqueous sodium silicate solution and a slightly concentrated aqueous sodium aluminate lye which contains 1 to 100 g Al ₂ O ₃ /! and 10 to 200 g Na ₂ O/! contains, optionally poured into a receiver of sodium hydroxide solution with a concentration of 0.1 to 500 g NaOH/l at the same time while stirring, the resulting synthesis premix with the composition SiO ₂ / AKO ₃ = 3.4 to 40 Na ₂ O/SiO ₂ = 0.2 to 0.5 and H ₂ O/ Na ₂ O = 4 to 40 is allowed to solidify to form a gel, a more highly concentrated aqueous sodium aluminate solution containing up to 200 g Al ₂ O ₃ /! and up to 250 g Na ₂ O/l is added to this gel at a temperature between 10 and 100 ⁰ C while stirring and the synthesis mixture thus obtained is allowed to crystallize at a temperature between 20 and 175°C within at least 15 minutes.

30

35

45

The invention relates to a process for producing a crystalline zeolite powder of type A with the composition

55

60 by hydrothermal crystallization of a sodium aluminal/water/silicate synthesis mixture containing SiO ₂ , Al ₃ O;, Na ₂ O and water with an optionally connected tempering step.

Zeolitic molecular sieves with their special properties for ion exchange and adsorption have been known for a long time. Their synthesis is based on heating an aqueous synthesis mixture with the components a Na ₂ OX b Al ₂ O ₃ xc SiO ₂ to temperatures between 50 and 300°C. Depending on the composition of the starting mixture, reaction temperature and reaction time, differently structured compounds of the general formula Na ₁ AI _x Si ₁ O,, ,.,&ldquor; · η H ₂ O are obtained, which can be distinguished by their X-ray spectra. Sodium can be replaced by other monovalent or divalent metal cations.

For use as adsorbents, catalyst supports or ion exchangers, the molecular sieves are converted into molded bodies using a suitable binder. The production of the molded bodies requires a great deal of technical effort, while at the same time reducing the effect due to the binder content. The long diffusion paths also significantly slow down the reaction rate, which makes drying organic liquids, for example, difficult. It is therefore sensible to use powdered molecular sieves for some applications.

The known manufacturing processes (e.g. DE-PS 10 38 017) have in common that during molecular sieve synthesis crystals are obtained whose average diameter is above approx. 2 μηι, whereby a significant proportion, usually between 3 and 12% by weight, has a limiting grain size of over 45 μm. This proportion is referred to as grit, which is determined according to DIN 53 580 by wet sieving according to Mocker. In a product typical for this process, it can be determined that approx. 25% by weight of particles have a diameter of less than 10 μηι, 50% by weight have a particle diameter of 13 μγι. (D. W. B reck. Zeolite Molecular Sieves, p. 388, John Wiley + Sons, New York-London, Sydney, Toronto, 1974.)

The invention is based on the task of developing a process with which powdered, zeolitic molecular sieves of type A without grit (particles <45 μg) and with smaller grain sizes can be synthesized, in particular for use as ion exchangers, e.g. for water softening. The absence of grit and a smaller grain size are essential for the use of such molecular sieves, among other things as a phosphate substitute in washing, dishwashing and cleaning agents. Washing and cleaning processes, in particular in machines, require the molecular sieve to remain suspended in the liquor (due to a low tendency to sedimentation) in order to enable complete rinsing after the process has ended.

The invention relates to a process for producing a crystalline zeolite powder of type A with the composition

1.0 ± 0.2 Na ₂ O: Al ₂ O.,: 1.85 ± 0.5 SiO ₂ · y H ₂ O,

where r means a value of up to 6, with at least 99.5 wt.% of particles below 30 μm in diameter and with at least 90 wt.% of particles below 10 μm and with 50 wt.% of particles below 6.5 μm at most and with a particle spectrum

fraction

Share (% by weight)

<5

<20

25-35
90-93
91-97
93-98

IO

by hydrothermal crystallization of a sodium aluminate/water/silicate synthesis mixture containing SiO ₂ , Al ₂ O ₃ , Na ₂ O and water, with an optionally connected tempering stage, which is characterized in that an aqueous sodium silicate solution and a slightly concentrated aqueous sodium aluminate solution containing 1 to 100 g Al ₂ O ₃ /l and 10 to 200 g Na ₂ O/l are optionally poured together simultaneously with stirring into a receiver of sodium hydroxide solution with a concentration of 0.1 to 500 g NaOH/l, the resulting synthesis premix with the composition SiO ₂ /Al ₂ O, = 3.4 to 40 Na ₂ O/SiO ₂ = 0.2 to 0.5 and H ₂ O/Na ₂ O = 4 to 40 is allowed to solidify to form a gel, a more highly concentrated aqueous Sodium aluminate solution containing up to 200 g Al ₂ O ₃ /l and up to 250 g Na ₂ O/l is added at a temperature between 10 and 100 ^° C with stirring and the synthesis mixture thus obtained is allowed to crystallize at a temperature between 20 and 175 °C within at least 15 minutes.

Preferably, the temperature during crystallization is 100 ^° C.

The synthesis mixture resulting from the addition of the sodium hydroxide solution can contain the individual particles in molar ratios as used in known processes. Such known processes are described in DE-PS 10 38 017 and DE-AS 10 95 795.

While the crystallization in the present case can be carried out at 93°C, for example, it has proven advantageous to carry out the tempering at a temperature between 85 and 105 ^° C in the crystallization mother liquor, with tempering times between 0.8 and 1.0, in particular one hour, being favorable.

The tempering time begins at the point at which crystallization is complete, as indicated by the development of maximum ion exchange capacity, the achievement of maximum X-ray line intensity and the achievement of approximately 22.5% water vapor adsorption. In practice, an empirical value determined by recipe optimization is used as a basis.

The crystalline zeolite powder of type A produced according to the invention can be used as a phosphate substitute in washing, dishwashing and cleaning agents.

Such detergents are combinations of surface-active washing raw materials, but usually also contain other, mainly inorganic additives that contribute to the washing success or are necessary for the manufacturing process and the external properties of the product. The composition of the detergents varies according to the intended use, in particular it depends on the type of fiber, color and washing temperature, as well as on whether the laundry is washed by hand, e.g. in a boiler, in a household washing machine or in a laundry. Most detergents are pourable powders. However, there are also liquid and paste-like products (see Ullmanns Encyklopädie der technische Chemie, 3rd edition, volume 18. Urban + Schwarzenberg, Munich, 1967).

The crystalline zeolite powder of type A produced according to the invention has the advantage that it is grit-free and contains smaller particles when it is produced. When used as a phosphate substitute in washing and cleaning agents, it can therefore be easily kept suspended in the respective liquors and can be particularly easily rinsed out of washing and cleaning machines and their loading.

The process according to the invention is explained in more detail below using examples:

I. Production
of type A crystalline zeolite powder

example 1

50 l of sodium hydroxide solution containing 60 g Na ₂ O2l are placed in a 2 m' trough.

While stirring, 125 l of water glass solution containing 26.5 wt.% SiO _: and 8 wt.% Na ₂ O and 125 l of sodium aluminate lye containing 60 g Na _: 0/l and 20 g Al 7 O 3 /l are simultaneously added to the sodium hydroxide solution at room temperature at a rate of 5 l/min.

After a short time (approx. ¹ Ah), the initially clear solution forms a gel to which 900 l of a sodium aluminate solution at 80 ⁰ C, which contains 100 kg of commercially available aluminum oxide hydrate (wet hydrate) with a water content of 42.5 wt.% and 92 kg of NaOH, is added while stirring. The reaction mixture is allowed to crystallize at 93°C for 3.5 h. The crystalline product is X-ray-pure zeolite A with the following grain spectrum:

fraction Portion (;&lgr;&Ggr;&Pgr;&Igr; (Weight-"...) < 5 25 <10 93 <15 97 <20 98

where 50% by weight have a grain size of less than 6.5 μm. A sedimentation balance is used in all examples to determine the correction spectrum.

Example 2

50 l of sodium hydroxide solution containing 60 g Na ₂ O/! are placed in a 2 m ^J trough.

While stirring, 120 l of water glass solution containing 26.5 wt.% SiO ₂ and 8 wt _. % Na 2 O 3 and 110 l of sodium aluminate solution containing 60 g Na ₂ O 3 /l and 30 g Al ₂ O 2 /l are simultaneously added to the sodium hydroxide solution at room temperature at a rate of 5 l/min.

After a short time (approx. _1/2 h) the initially clear solution forms a gel to which 900 l of a sodium aluminate solution at 80 ⁰ C, which contains 150 kg of commercially available aluminum oxide hydrate (wet hydrate) with a water content of 42.5 wt.% and 138 kg of NaOH are added.

while stirring. The reaction mixture is allowed to crystallize at 93°C for 3.5 hours and the crystalline product obtained is X-ray pure zeolite A. The white powder has the following particle size spectrum:

fraction Portion ( JlII &bull; Weight:.) < 5 35 <10 91 <15 95 <20 96

10

15

where a proportion of 50 wt. "/» is less than 6 µm grain size.

Example 3

20

While stirring, 85 ml of water glass solution containing 26.5 wt.% SiO ₂ and 8 wt.% Na ₂ O and 85 ml of sodium aluminate solution containing 60 g Na ₂ O/! and 20 g Al ₂ O ₅ /! are simultaneously metered into a 11-capacity round-bottom flask at a rate of 100 ml/min.

After a short time, the initially clear solution forms a gel.

A sodium aluminate solution containing 70 g of commercially available aluminum oxide hydrate (wet hydrate) with a water content of 424% by weight, 63 g of NaOH and 300 ml of water is added to this gel at room temperature while stirring.

The resulting reaction mixture is heated to 93 to 95°C and kept at this temperature for 2 hours to crystallize. The resulting crystalline product is X-ray pure zeolite A and has the following grain spectrum:

fraction
(around)

Proportion (wt.%)

< 5

35
90
92

40

45

e.g. by hot drying, the composition:
21.0% by weight ABS (dodecylbenzenesulfo-

nat);

7.5 wt.-"O ethoxylated tallow alcohol (1 mol tallow alcohol + 14 mol ethylene oxide);

7.2% by weight soap (sodium salt of saturated, mainly C1-C4-fatty acids);
9.0 wt.% water glass (Na ₂ O - 3.3

_SiO2 );

4.5 wt.% magnesium sulfate;
2.0% by weight carboxymethyl cellulose;
0.6 wt.% optical brightener;
9.0 wt.% soluble complexing salt (e.g., sodium citrate, sodium triphosphate);
35.0 wt.% sodium sulfate;
Rest Wassp t

The detergent is made by mixing the three powdered ingredients.

Example 2
Perborate-free detergent

2.0% by weight of ethoxylated d/cis-oxoalcohol

(1 mole oxo alcohol + 3 moles ethylene oxide);*)
5.0 wt.% ethoxylated Q i/C _i5 -oxo alcohol

(1 mole oxo alcohol + 13 moles ethylene oxide);**)·

40.0 wt.% sodium aluminium silicate, obtained according to Examples I, 1 to 3
(dried for 6 hours at 90 ⁰ C, water content 16.8 wt.%)
15.0% by weight soda;
5.0% w/w sodium citrate;
4.0 wt.% water glass (Na ₂ O · 3.3 SiO ₂ );
1.5% by weight carboxymethyl cellulose;
0.2 wt.% optical brightener;
23.0 wt.% sodium sulfate;
Rest water.

<20 94

*) can be replaced by tallow alcohol + 5 moles of ethylene oxide; **) can be replaced by tallow alcohol + 14 moles of ethylene oxide, whereby a proportion of 50% by weight is less than 6.3% of the grain- 50

size. The detergent is applied by spraying the ethoxy

lation products (non-ionic surfactants) onto the powder particles, consisting of the remaining components.

II. Use of the inventive

manufactured crystalline zcolith powder of type A

example 1
Detergent containing perborate

45.0 wt.-"/,. Sodium aluminum silicate, obtained according to

Examples I, I to 3

((> hours at 90 ⁰ C, water- «.5

content 16.8 wt.-",;,)
20.0 Ciew.-",,, Niilriumperboral;
35.0 wt.-". of a detergent powder, manufactured

Claims (1)

Patent claim: Process for the preparation of a crystalline zeolite powder of type A having the composition 1.0 ± 0.2 Na ₂ O: Al ₂ O ₃ : 1.85 ± 0.5 SiO ₂ - y H ₂ O, where y is a value up to 6, with at least 994 wt.% of particles below 30 μηι diameter and with at least 90 wt.% of particles below 10 μηι and with 50 wt.% of particles below 6.5 μm at most and with a particle spectrum