DE1567888C - Process for the preparation of crystalline zeolite Y. - Google Patents

Description

The invention relates to a process for the preparation of zeolite Y using reaction systems with low silica and water content. .;

Zeolite Y is a synthetic crystalline aluminosilicate of the so-called molecular sieve type, which is characterized by the fact that it structurally consists of a three-dimensional lattice structure of SiO ₄ and AlO ₄ tetrahedra, which is cross-linked by oxygen atoms and contains internal spaces containing molecules with certain critical dimensions to adsorb

ίο fortune. Regarding the chemical composition Common crystallized zeolite Y is characterized by the following formula:

0.9 ± 0.2 Na ₂ O: Al ₂ O ₃ : w SiO ₂ : λ: H ₂ O.

Herein, w has a value of more than 3 up to 6 and χ has a value of up to 9. By treatment with acids or a chelating agent selected from a large number of suitable chelating agents, e.g. B. with acetylacetone, the value of w can be increased significantly by selective removal of aluminum from the crystal structure without destroying the characteristic X-ray diffraction pattern of the freshly produced crystal. This diffraction pattern has essentially the values given in Table A below. the

The values for the interplanar distance d are expressed in angstroms.

Table A.

hkl 111 ? 55 10, 5, 5 " } 10 8 6 * · + * · + / ■ dk 14.15 Relative intensity 220 11, 5, 5; 993 J. 3 14.37 to 8.67 very strong 311 977 8th 8.80 to 7.39 medium ι 331 1; 11th 7.50 to 5.62 medium 333,511 9
1· 19th 5.71 to 4.72 strong 440 3; 27 4.79 to 4.33 medium 531 32 4.46 to 4.16 medium 600.442 5 35 4.29 to 4.09 weak 620 n 36 4.13 to 3.88 weak 533 5 40 3.93 to 3.74 weak 631 43 3.79 to 3.62 strong 711, 551 46 3.66 to 3.43 medium 642 51 , 3.48 to 3.28 very weak 733 56 3.33 to 3.00 strong 822, 660 ~ 67 3.04 to 2.89 medium 751, 555 72 2.93 to 2.83 medium 840 75 2.87 to 2.74 strong 911.753 80 2.78 to 2.69 medium 664 83 2.73 to 2.61 weak 844 88 2.65 to 2.50 medium 10, 0, 0; 860 96 2.54 to 2.45 very weak 10, 2, 0; 862 100 2.49 to 2.40 very weak 10, 2, 2; 666 104 2.44 to 2.36, very weak 10, 4, 0; 864 108 2.39 to 2.25 medium 11,1,1; 775 116 2.29 to 2.21 very weak 880 123 2.24 to 2.17 very weak 11.3, 1; 971; « 128 2.20 to 2.14 weak 11, 3, 3; 973 131 2.18 to 2.08 very weak 12, 0, 0; 884 139 2.11 to 2.04 weak 11, 5, 2; 10, 7, 144 2.07 to 2.00 very weak 10.8.2
13, 1.1; 11, 7, 150 2.03 to 1.89 very weak 13, 3.1; 11, 7, 168, 171 1.92 to 1.83 very weak 13,3,3; 995
888 179 1.86 to 1.79 very weak 13, 5, 1; 11, 7, 187, 192 1.82 to 1.76 very weak 14, 2, 0; 10, 10 195 1.78 to 1.73 very weak 13, 5, 4; 11, 8, 200 1.76 to 1.69 weak 210 1.71 to weak

Zeolite Y is extensively described in U.S. Patent 3,130,007. There is also described the process used to prepare zeolite Y, which generally consists of aging, digesting and crystallizing an aqueous sodium aluminosilicate mixture, the proportions of the reactants being expressed in moles of Na ₂ O, H ₂ O, Al ₂ O ₃ and SiO ₂ mainly depend on the raw material,

which was selected as the silicon support for the reaction system. For example, if sodium silicate, Silica gels or silicic acid used as silicon source must be the aqueous sodium aluminosilicate reaction system in terms of molar ratios of oxides fall within one of the ranges given in Table B below.

Table B.

Area a Area b

Area c

Na _a O / SiOs
SiO ₂ / Al ₂ O ₃
H ₂ O / Ha ₂ O

0.6 to 1.0

8 to 30

12 to 90

1.5 to 1.7
10 to 30
20 to 90

1.9 to 2.1 about 10 40 to 90

If an aqueous colloidal silica sol or ao silica and for the remainder sodium silicate verkihi f Kil l d d fü d Gih fld Z

If a reactive amorphous solid silica is used as the silicon support, the molar ratios must be used the oxides fall into one of the ranges in Table C.

table C

Na ₂ O / SiO _a
SiO ₂ / Al ₂ O ₃
H ₂ O / Na ₂ O

Area d

0.28 to 0.30

8 to 10

30 to 50

Area c

about 0.4 10 to 27 30 to 50

Zeolite Y is recognized as one of the most versatile and effective synthetic crystalline molecular sieve zeolites has been recognized for both adsorption and catalysis purposes, but it is one of the Zeolites, the most difficult to obtain in consistently high purity and in high yields on the starting materials' are to be emphasized. ,

According to Belgian patent specification 598 968, kaolin is primarily used as the starting material. The composition of the reaction mixtures is outside the ranges according to the invention. The German patent specification 1295 533 describes a process that starts from reaction mixtures with a low Na ₂ O content. The lowest ratio of H ₂ O: Na ₂ O reached is 14.8. Both cited processes use aqueous mixtures of the reactants.

The invention, however, is a process for the production of zeolite Y from a Reaction system based on dry gel mixtures, which has a more effective composition that to a higher yield of zeolite Y per unit weight of the silicon support used and to one increased, volume-based efficiency of the apparatus than those previously used Reaction systems. The process according to the invention has significant economic advantages, since the hydrothermal treatment can be carried out with devices designed for processing Solids are used.

The method according to the invention for the preparation of crystalline zeolite Y by hydrothermal Treatment of aqueous sodium aluminosilicate mixtures is characterized by having as a source of at least 80 mole percent of the silica Solid reactive amorphous in the mixture and the following composition for the mixture complies with:

Na ₂ O / SiO ₂ 0.2 to less than 0.6 SiO ₂ / Al ₂ O ₃ 3.5 to 7
H ₂ O / Na ₂ O 8 to 13.

The reaction mixture is at least 6 hours,

preferably 8 to 48 hours, aged at room temperature before being brought to elevated 'temperature will. The elevated temperature is maintained until crystals of zeolite Y have been formed.

For supplying the required reactive form of silicon, aluminum and sodium .Zum reaction system have been found to be compounds that have hitherto been used in conventional processes for the preparation of Zeolite Y were also used as being suitable for the process according to the invention. aluminum in the form of activated aluminum oxide, y-aluminum oxide, Aluminum trihydrate, aluminum oxide gels, aluminum oxide sols and sodium aluminate, silicon in the form of solid amorphous silicon dioxides, such as vapor phase silica, chemically precipitated silicas, silica, silica gels, silica sols and sodium silicates and Sodium in the form of sodium hydroxide, sodium aluminate or sodium silicate are all suitable Reagents. A solid, amorphous silicon dioxide with a medium level is preferably used as the silicon carrier Particle size below about 1.0 microns. Alumina trihydrate is wildly preferred as the aluminum source and sodium hydroxide as the sodium source.

If the reactants are brought together to form the reaction system from which zeolite A crystallizes, the order of mixing is not critically important. Although all reaction systems within the scope of the invention are "wet" gels, ie they can be processed in apparatuses that are suitable for handling flowable media, systems at the lower end of the range of the H "O / Na ₂ O- As a result, when a solid amorphous silicon dioxide is used as the silicon carrier, a uniform composition is sometimes not achieved immediately in all the sequences of mixing. Accordingly, in order to obtain a reaction system of perfectly uniform composition, it has been found useful to form the final composition by adding a slurry of the solid amorphous silica

is mixed with a solution of the sodium aluminate in water. When sodium aluminate is used as the aluminum support, its aqueous solution is formed simply by adding a portion of the total amount of water required to the sodium aluminate. However, when alumina or aluminum trihydrate should be used, the sodium aluminate solution is prepared by this reagent is dissolved in an aqueous sodium hydroxide solution at about 90 ⁰ C. It is advantageous to cool the sodium aluminate solution thus formed to about 30 ° C. before mixing it with the aqueous slurry of solid amorphous silicon dioxide.

As with the usual known processes for the production of zeolite, it has proven advantageous to age the gel by allowing it to stand quietly at ambient temperature (about 23 ° C.) for about 8 to 48 hours. The higher the silicon dioxide-aluminum oxide, the longer the aging time. Ratio is. The temperature is then increased in the range from about 80 to 120.degree. C., preferably to about ^100.degree. C., whereupon the digestion and crystallization are allowed to take place for about 48 hours. A digestion time of only about 5 hours has been used, but a time of about 20 to 48 hours is preferred.

The crystals of zeolite Y are washed with pure water until the washing water running off has a pH value of less than 8. The crystals are then dried and activated at temperatures of about 300 to 450 ⁰ C. When a solid reactive amorphous silica is a reaction mixture containing an aqueous sodium aluminate silicate, the source of at least 80 mole percent of the silica in the mixture and the remainder being provided by sodium silicate, a reactant mixture having a very low water content can be used. The process according to the invention is described in more detail with the aid of the following examples.

Example 1 and 2

Using an amorphous solid silica as the silicon support, aluminum trihydrate as the aluminum support, and sodium hydroxide (76 percent by weight Na ₂ O) as the sodium source and of

ίο water, 2 reaction systems were produced as follows

. placed: ..·'..

. A sufficient proportion of all the water used was used to dissolve the sodium hydroxide. The aluminum trihydrate was added to this solution and ^{heated to 90 °} C. for a sufficient time to dissolve the aluminum trihydrate and to form sodium aluminate with the available sodium. The silica was stirred into the rest of the water and added at a temperature of 30 ⁰ C to the sodium aluminate solution. In order to achieve a uniform mixture, a heavy kneader or a ribbon mixer equipped with a cooling jacket was used vigorously. The resulting dry gels were 8 to 48 hours

Aged at room temperature and then digested for 48 hours at 100 ° C. Depending on the sodium hydroxide content, the crystalline product (zeolite Y) was either washed until the pH of the washing water running off was 8, or was not subjected to any further treatment. In all cases, the structure of zeolite Y was determined by conventional X-ray analysis. The compositions of the respective reaction systems, expressed in molar fractions and in molar ratios of the oxides of sodium, aluminum, silicon and hydrogen, the approximate percentage of zeolite Y in the crystallized product and the SiO ₂ / Al ₂ O ₃ ratio of the zeolite Y formed are in the following Called table.

example
No.

Molfraction of the gel

SiO ₂

AUO ₃

Na ₂ O

H ₂ O

Mole

Mole

Molar ratios

NajO / SiO,

SiOJAl ₂ O ₈ H _a O / Na _{2 O}

Product unit (%)

X-ray analysis

O ₂ /
Adsorption*)

SKyAl ₂ O ₃
in the product

0.570
0.702

0.130
0.106

0.300
0.192

2.5
2.5

0.526
0.274

4.38 6.67

95.8
100

98.0
88

*) 100% zeolite Y = 34.5% O ₂ adsorption at 100 mm Hg and -183 ° C.

3
4.76

Claims (2)

Patent claims: 1. Process for the preparation of crystalline zeolite Y by hydrothermal treatment of aqueous sodium aluminosilicate mixtures, d a duich characterized that one as Source of at least 80 mole percent of the silica in the mixture being solid reactive amorphous Silicic acid and sodium silicate for the remainder and the following composition for the mixture complies with: Na ₂ O / SiO ₂ 0.2 to less than 0.6
SiO ₂ / Al ₂ O ₃ 3.5 to 7
H ₂ O / Na ₂ O 8 to 13. 2. The method according to claim 1, characterized in, that the reaction mixture at least 6 hours, preferably 8 to 48 hours Room temperature is aged before it is brought to elevated temperature.