DE2435716A1 - PROCESS FOR THE PRODUCTION OF HEAT AND ACID RESISTANT ZEOLITHES FROM ALKALIFAUJASITES - Google Patents

Description

Our mark O.Z. 50 672 Vo / Wil 6700 Ludwigshafen, July 18, 197 ^

Process for the production of heat and acid resistant Zeolites from alkali faujasites

The invention relates to a method mr production of heat and acid resistant faujasites. The procedure persists in a gradual replacement of the alkali ions of the alkali faujasite by ammonium ions with intermediate calcination and final alignment and, if necessary, rait a final Acid treatment,

There exists in the art a need for wi: RKSP "3n temp" ratur- and acid-resistant catalysts or adsorbent ₉ !! on ZeolithbasiSp because many katalytisehe processes and absorption processes carried out in an acidic reaction medium

become _β

The stability of zeolites against heat, water vapor and Acids are all the greater, the higher the SiOg / AlgO ^ molar ratio is. Therefore one finds in the series from A to X, Y and D zeolite an increase in persistence.

To increase the acid stability of zeolites, ie the Si0 ₂ / Alg0 ₃ ratio, the DAS 1 46? 1 ^ 9 suggested to convert the zeolite at least partially into the hydrogen form and then to dissolve the aluminum from the crystal lattice h @ with a complexing agent. In this way, the SiOg / AlgO ^ molar ratio of the zeolite is

increases and you can get products after the exchange, which are more resistant to acid than the starting materials. Of the The disadvantage of this process is that the crystallinity of the starting material is noticeably reduced (see example 15 of the DAS quoted).

In the fe ^ gaagenen Jalarsn mrclen procedure developed * - naoh which lögeaamit® laltrastabile Fatajasit © are provided

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can. Such processes are described in the laid-open German patent application 2,052,4-5 and in US Pat. No. 3,449,070 and 3,293,192. According to this process, Y-Ze © · »is obtained. lithe "which are stable up to a temperature of about 1000 ⁰ C. At this temperature, the so-called crystal lattice collapse "do h _e done the zeolite becomes amorphous ,, The continuous power is the temperature * these zeolites long periods without structural collapse withstand graining ^ is low, it is about 920 ⁰ C.

However, there is a need as zeolites for cracking reactions and as heat and steam resistant carrier materials, e.g. For example, for catalysts in the Äutoabgasentgiftung whose temperature stability contributes continuous load at least 1000 ⁰ C be ~ "Besides, there is a need in acid-resistant faujasites !! * which can be smaller than adsorbents and catalysts also at pH values used as the fourth The present invention is based on the object of providing a process for the preparation of these compounds. It was surprising and unforeseeable that it would be possible to meet the two aforementioned requirements at the same time.

The present invention therefore relates to a process for the production of heat-stable and acid-stable zeolites from alkali faujasites, which have a SiOg / AlgQ molar ratio of 4.0 to 7, by first exchanging the alkali ions of the faujasite for ammonium ions, subsequent calcination, renewed ion exchange and repeated calcining. This method is characterized in that down to a residual content of 7 bis'5% (calculated as Ma ₃ O) exchange in the first replacement step, the alkali metal ions, filtered, and-without drying at temperatures ¥ on TOO to 800 ⁰ C calcinlert, Then in the further exchange stage the alkali ions are exchanged to a residual content of less than 2 ^ 5 ^ (calculated as Ma ₃ O) and calcined without drying at temperatures γ @ η 300 to 900 ⁰ C and the product thus obtained is optionally an aqueous solution treated with a strong mineral acid and the product obtained is filtered, dried and optionally salci-

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ned.

The present invention relates in particular to a process for the production of heat = · and acid-stable defect zeolites with a SiOg / AlgCU molar ratio of greater than 7: 1 from alkali faujasites ^ which have a SiOg / AlgCU molar ratio of 4.5 to 6, by first exchanging the alkali ions of the faujasite for ammonium ions *, subsequent calcining, renewed ion exchange and repeated calcining. This process is characterized in that in the first exchange stage the alkali ions are exchanged to a residual content of 2 to 4 % (calculated as Ma ^ O), filtered and ^{calcined without drying at temperatures of 400 to 70O 0} C, then in the further Äustauschstufe the alkali metal ions to a residual content of below 1.5 # (calculated as Na ₂ O) exchanges and without drying at temperatures iron 800 to 900 ⁰ C calcined and treating the product thus obtained with an aqueous solution of a strong mineral acid, the product obtained in this way is filtered, dried and, if necessary, eaten

The inventive method Iganm. also modified as follows will?

In the second level a suitable buffer, ^{capable of exchanging NH ^ +} , can be used. This should have a pH in the range "from J ₅ 5 to 6 _P 5 ; in particular the ammonium acetate / acetic acid system in the pH range from 3 * 5 to 4 ^ 5 has proven to be suitable. Even in the first exchange stage, with this buffer system can be used * if the pH of the solution is adjusted to values greater than 4.5 and the Si0 ₂ / Al ₂ 0, ratio in the starting seolite is at least 5.6 »

Can be used as starting materials for the process according to the invention natural or synthetically produced alkali faujasites with a molar ratio of SiOg / AlgO-, of greater than 4.0 ver. be turned. Alkaliberyllo-silicates of the Paujaslttyp, as described in German patent application P 22 56 450.7 OoZ. 29 531 are described as well as those from these beryllium

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Defect zeolites produced by zeolites (see patent application P? ϊ? § i§? * 5- 0.Zo 30 601) are used as starting materials for the process suitable »Aqueous solutions of ammonium salts are preferably used for ion exchange. There come in particular Ammonium chloride, ammonium sulfate, ammonium nitrate and ammonium carbonate to be considered »Also ammonium salts of organic acids like acetic acid or formic acid can be used for ion exchange »

In the first exchange stage, the alkali content of the zeolite is reduced from originally around 13% to a value of around 7 to 5%, calculated as Na ₂ O. % Alkali, calculated as Na ₂ O, reduced.

Between and after these exchange stages there is a calcination stage. The first step of calcination is carried out at temperatures of 700 to 800 ° C, in the second step of calcination, higher temperatures can be used in accordance with the lower alkali content of the faujasite. 800 to 900 ^° C. are preferably chosen. The following rule applies to calcining? The greater the SiOg / Al ^ jOv molar ratio of the zeolite, the higher the calcination temperature that can be selected in the aforementioned ranges. The higher the sodium content, the lower the calcination temperature must be chosen. It is important that this temperature is chosen so that the crystal lattice of the zeolite does not collapse, i.e. the zeolite does not become amorphous.

Following the exchange stages, the product obtained is in each case filtered and caleined without prior drying Is very essential that the material for the caleination stage is used while it is still wet, otherwise the grid can collapse. If still after the acid treatment should be caleined, it can also be dried beforehand. In this case there is no longer any risk of a grid collapse

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given »

Usually 1 to 6 normal mineral acids such as nitric acid, hydrochloric acid or sulfuric acid are used for the acid treatment applied The calcined product from the previous stage is introduced into the aqueous solution of the acid and left in it for 1 to 10 hours.

This treatment removes some of the aluminum atoms from the tetrahedral sites in the zeolite framework. The vacated tetrahedral sites are stabilized with the help of water molecules and protons; this creates defects in the gross composition of HnOp. That is, the SiOg / AlpO - ^ - molar ratio of the starting materials is increased by the process according to the invention. The products obtained from the starting materials are therefore referred to below as defect zeolites. The acid treatment can, if deemed necessary, also be carried out at higher temperatures, e.g. B. up to 100 ^° C. Products can be obtained which, for. B. with a SiOp / AlpO ^ molar ratio of more than 60 still have an Al _o 0 ^ content of about 2 to 4 % . Their lattice constant

ο is about 24.20 A. Finally, the aluminum can also be completely removed. A new, defined modification of the silicon dioxide hydrate is formed, which contains defects in its crystal lattice. With this new modification, the defects can be filled with silicon atoms by calcining at 800 to HOO ^{0 C without damaging the crystal lattice.} During the calcination, a new SiOg modification with a paujasite structure is created, in which there are no longer any defects.

According to the process according to the invention, zeolites can be produced which are characterized by the following properties:

1. a lattice constant of less than 24.40 A «

2. a surface area of about 500 to 900 m ² / g

3. A long-term temperature resistance of 1000 to HOO ⁰ C

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4. Resistance to acids

5. one that is not significantly reduced in relation to the starting material Crystallinity

6. SiOp / AlpO ^ molar ratio greater than 7 * if after the second calcination stage the zeolite is treated with an acid.

The acid treatment further increases the thermal stability. It is enough to have one Increase the SiOp / AlpO ^ molar ratio to more than 7, to achieve a significant increase in temperature stability and acid resistance. As a particularly heat and acid-resistant, defect zeolites with a SiOg / AlgO-v molar ratio of greater than 8 to 10. Extraordinary Finally, defect zeolites in which the SiOp / AlpO ^ molar ratio is more than 30, preferably, are heat and acid-resistant 60 to 70. Such molar ratios are unusual for faujasites.

In order to produce a defect cell with a SiOp / AlpO, molar ratio of up to 8 from the starting materials, the treatment with acids is omitted and the ion exchange, as already mentioned, in the presence of a buffer solution at pH values between 3 * 5 and 4.5 make. If an SiO ₂ / Al ₂ O molar ratio of more than 8 to about 30 is to be achieved, the acid treatment will be carried out in any case. After the acid treatment is filtered, dried and calcined ⁰ C, generally at temperatures of from 800 to HOO. Within this range, higher temperatures are chosen for the representatives with a low aluminum oxide content and lower temperatures for the representatives of aluminum oxide.

The zeolites produced according to the invention are strong proton donors and can advantageously be used as absorbents or catalysts.

The zeolites produced according to the invention fall in the H form at. If not all of the aluminum has been removed from their crystal lattice, the H ions can be treated with

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aqueous solutions of mono-, di- or trivalent metals are subjected to ion exchange. Make such zeolites then particularly reactive sorbent masses or catalysts. The invention is illustrated by the examples below explained in more detail.

example 1

150 g of a sodium aluminosilicate of the faujasite type with an Na content of 10.6 wt.% And a SiO ₂ Zal ₂ O ₅ -MoIverhältnis, 4.4 (Y-zeolite) was subjected to the ammonium exchange. The zeolite was treated at room temperature for about 5 minutes with a solution of I50 g of ammonium carbonate in 2000 ml of water .. The zeolite was filtered and caleiniert 3 hours at 770 ⁰ C. The Na _p 0 content after this treatment was 5> 3% by weight, the lattice constant was determined by X-ray to be 24.613 Å.

The ammonium exchange with an aqueous ammonium chloride solution was then repeated until the Na ₂ O content was reduced to about 1%. The zeolite was then filtered, washed free of chloride and ^{calcined at 870 °} C. for 3 hours. Its lattice constant was then 24.362 A; the temperature of the collapse of the lattice, determined radiographically with the aid of a Lenne-Guinier high-temperature camera, was 99O ⁰ Cj and the surface was determined to be 800 m ² / s.

Examples 2 to 5

Some samples of the zeolite obtained in Example -1 were subjected to an acid treatment to remove the aluminum from the crystal lattice.

The test results are compiled in the table. It can be seen that the thermal stability is increased even further after the acid treatment has been carried out. the The crystallinity of the zeolites is increased by the acid treatment not significantly reduced. The crystallinity of the samples was determined by X-ray and related to the crystallinity of the starting zeolite. The intensity of the inflection line

■ ο
at d ~ 14.3 - 0.4 A, 100 was set. It deals

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These details refer to relative crystallinities. One
An indication of crystallinity of greater than 100 % is due to the fact that the structurally determined intensity of the reference line is greatly increased by the method described.

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TABEL

cn O CO CD CD cn

cn

CO

example 1 - 2 3 4th 5 treatment before the 35 g zeolite 35 g zeolite 6 g of zeolite 3 g of zeolite Treat 1000 ml 3n- 1000 ml of 3N HCl 100 ml in- 120 ml of 6N HCl lung ENT, 3 hours HCl 5 hours j
3 hours
50 to 6O ⁰ C 70 ⁰ C 500 ml H ₀ O
3 hours
20 ⁰ C 100 ⁰ C .0.
Lattice constant (A) 24,362 24.282 24.24 24.304 24.257 Crystallinity (#) - 130 130 170 90 Lattice Collapse ( ⁰ C) 990 "1050 > 1050 > 1050 + Surface (m ² / g) 800 710 680 800 + SlOg / Al ^ -Molver- ratio 4.4 72 62 16.6 > 100 Lattice constant (A) after calcination at 85O ⁰ C 24,168 24.219 + +

VO

+ = not measured

VjJ O

CTN ro

cn

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Example 6

As described in Example 1, an ammonium carbonate solution was used to lower the NagO content of an alkali faujasite to about 6 %; Thereafter, the zeolite was calcined for 3 hours at 75O ⁰ C.

In the second step of the ammonium exchange process, an ammonium acetate-acetic acid buffer solution of the following composition was then used used:

819 g ammonium acetate, 2100 ml acetic acid (98 # lg) and 6000 ml water on 150 g zeolite. The zeolite was then filtered, washed acetatfrei and calcined for 3 hours at 87O ⁰ C. the

, ο

Lattice constant was 24.31 Aj the temperature of the grid collapse was determined to be 1020 ⁰ C.

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Claims (2)

Claims (£), Process for the production of heat- and acid-stable ^ n zeolites from alkali faujasites, which have a molar ratio Al ₂ O, of 4.0 to 7, by a first exchange of the alkali ions of the faujasite for ammonium ions, subsequent calcination, renewed ion exchange and repeated calcination, characterized in that in the first exchange stage the alkali ions are exchanged to a residual content of 7 to 5 # (calculated as Na ₃ O), filtered and calcined without drying at temperatures of 700 to 800 ⁰ C, then in the In a further exchange stage, the alkali ions are exchanged to a residual content of less than 2.5 % (calculated as Na ₂ O) and calcined without drying at temperatures of 800 to 90O ⁰ C and the product thus obtained is optionally treated with an aqueous solution of a strong mineral acid, the product obtained is filtered, dried and optionally calcined. 2. Process for the production of heat- and acid-stable defect zeolites with an Si0 ₂ / Al ₂ 0, molar ratio of greater than 7: 1 from alkali faujasites, which have a molar ratio SiOg / AlpO of 4.5 to 6, by a first exchange of the alkali ions of the faujasite for ammonium ions, subsequent calcination, renewed ion exchange and renewed calcination, characterized in that in the first exchange stage the alkali ions are exchanged to a residual content of 2 to 4 # (calculated as Na ₂ O), filtered and without, to dry at temperatures of 400 to 700 ⁰ C calcined, the alkali metal ions then in the other exchange stage to a residual content of below 1.5% (calculated as Na ₂ O) to exchange and drying at temperatures of 8OO to 900 ⁰ C calcined with and without the product thus obtained is treated with an aqueous solution of a strong mineral acid, and the product obtained is filtered, dried and optionally calcined. ^ * Zeiohn. ^ BASF Aktiengesellschaft 5 0 9 8 8 6/0673 _r