DD207186A1 - METHOD FOR THE PRODUCTION OF HIGH-KESELIC ACID-CONTAINING ZEOLITHES OF TYPE ZSM-5 - Google Patents

Abstract

The invention relates to an improved process for the preparation of crystalline Zsux-type cellosis-containing ziolites. In this case, a moving or static reaction mixture - consisting only of sources of alkali and / or alkaline earth metal oxide, alumina, silica and water - crystallized at elevated temperature and elevated pressure. The crystallization products in the dehydrated state have a composition expressed in moles of the oxides of (0.8 to 1.5) M below 2 / nO times AL below 2 ounces 3 times (20 to 80) SiO below 2 and may be in a pure form or in mixture with other substances as filler, adsorbent, ion exchanger and catalyst or catalyst carrier application.

Description

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WP C 01 Β / 237 602/3

Title of the invention;

Process for the preparation of high-silica-containing zeolites of the ZSM-5 type

Field of application of the invention

The invention relates to a process for the preparation of crystalline siliceous zeolites of the type 2SM-5, which can be used both in pure form and in mixtures with other substances as filler, adsorbent, ion exchanger, catalyst or catalyst support. «

Characteristics of the known technical solutions

Silicon-rich zeolites, e.g. the types Y, erionite and mordenite, have found increased application in hydrocarbon conversion catalyst systems. Due to the strong acidic centers of these zeolites, caused by the built-in aluminum grid, one of them, however, initiates side reactions which lead to an inactivation of the zeolites. In recent years, therefore, siliceous zeolites have been developed, e.g. the ZSM zeolites, which do not possess these disadvantageous properties and in particular by an increased Thermostabil! did, distinguished improved stability and a hydrophobic designated surface.

The high-siliceous SSLI zeolites are prepared by conventional synthesis technology from a Tleaktionsgemisch consisting of sources of alkali and / or alkaline earth metal oxide, alumina, silica and water in the presence of organic cations or their precursors by hydrothermal SjTithese at elevated temperature under autogenous pressure * As organic cations or their precursors, the zeolites of the ZSM series are preferably tetraalkylammonium compounds (US Pat. No. 3,702,586) or tetraalkyphosphonium compounds (DS-OS No. 2,813,969) * aliphatic amines (German Offenlegungsschrift No. 2,442,240) ) or diamines (DE-OS 2,818,576), choline (DS-OS 2,749,024), pyrrolidine (US Pat. No. 4,046,859) or pyrrolidone (US Pat. No. 4,010,642) and alcohols in combination with ammonia (DE-OS 2 913 552) for use

 These production methods for ZSH silicic acid-containing zeolites have the decisive advantage that on the one hand considerable amounts of the costly organic cations or their precursors are required for zeolite synthesis and, on the other hand, the organic cations after synthesis from the zeolites by calcination or ion exchange must be removed again to use the zeolites in catalyst systems can. Another ! Laughter in the use of organic cations is the additional technical security required and the z. T »strong odor nuisance, environmental pollution and health hazard in the processing of the synthesis products.

2s is also known "zeolitic molecular sieves" of the composition (0.9 to 3.0) M ₂ A ₁ O.AlgO-. (10 to 100) SiO ₂ . (0 to 40) H ₂ O, as they are referred to by the inventors in distinction to the ZSM zeolites, in particular ZSM-5, to produce from reaction mixtures which are free of organic cations (DE-OS 2,704,039). However, the products produced in this way are not compatible with the high

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siliceous ZSM zeolites, in particular the ZSM-5 zeolite, are identical since they have altered surface properties. This is demonstrated by adsorption and in the IR spectrum by the absence of the OH elastic vibration bands at 3100 to 3 00 cm ^-1 · Due to this property picture, the possible uses of these products, eg «as catalyst or adsorbent, are severely limited ·

Aim of the invention

The aim of the invention is to find an improved process for the preparation of high-siliceous zeolites of the type ZSM-5, which is technically simple to carry out and inexpensive.

presentation; the essence of the invention

It is an object of the present invention to provide a process for the preparation of crystalline zeolites containing high silica content of the ZSM-5 type which does not have the disadvantages and difficulties which are caused by the use of organic cations or their precursors in conventional synthesis technology.

According to the invention the object is achieved in that for the production of high-siliceous zeolites of the type ZSM-5 an aqueous reaction mixture at elevated temperature and elevated pressure necessary for the crystallization of the siliceous ZSM-5 zeolites time is maintained, the moving or stationary reaction mixture except a source of alkali and / or alkaline earth metal oxide, a source of alumina, a source of silica and water contains no further additives.

The sources of oxides may be z.sup.b; for alkali or alkaline earth metal alkali or alkaline earth metal hydroxides and / or alkali or alkaline earth metal

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metal salts,

alumina hydrated or hydratable alumina, aluminates and / or aluminum salts,

fumed or precipitated silica, silica sols, silica gels ₉ alkali metal silicates and / or aluminosilicates for silicon dioxide »

The mixing of the components may be carried out batchwise in the vessel intended for the reaction or continuously in a step upstream of the crystallization.

The high silica zeolites of ZSM ~ 5 type v / ground by the inventive process typically consists of moving the reaction mixtures of the composition ^ expressed in moles of the oxides, (2 to 50) M ^ y _n O · ^ 2 ° 3 "(10 to 300 SiO ₂ · (200 to 500) HgO, preferably from agitated or quiescent reaction mixtures of composition (3 to 20) M ₂ Jy _n O · Al ₂ O ₃ (15 to 150) SiO ₂ · (500 to 5OOO) H ₂ O and more preferably from agitated or quiescent reaction mixtures of composition (5 to 10) M _{2 / n} 0 .Al ₂ O _3. (40 to 60) SiO _2. (1000 to 25OO) H ₂ O, where M is an alkali metal or alkaline earth metal and η denote ertigkeit the Y /, Typical reaction conditions are a crystallization temperature of 80 to 200 ^0C, preferably of 150 to 180 ⁰ G, increased pressure and a crystallization time of 6 to 200 hours, and it is essential that a Temperature / pressure ratio of 0.1 to 5 K / kPa is maintained .Through 4 to 20 hours iges aging of the reaction mixture at room temperature, the crystallization time can be significantly shortened and the purity of the high-silica containing zeolites can be increased. The resulting zeolite crystals are separated from the mother liquor by methods known to those skilled in the art and further worked up.

- 5

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An essential advantage of the process according to the invention is that no organic cations or their precursors must be used. Thus, the expenses for the otherwise necessary organic compounds, the safety technology and the removal of the organic cations from the zeolite by z, B. Calcination or ion exchange accounts. Furthermore, no environmental pollution by organic compounds occur.

The zeolites of the type ZSM-5 prepared by the process according to the invention are free of organic constituents and have a composition in the dehydrated state, expressed in moles of oxides, of (0.8 to 1.5) ^M p / n ° * Al ₂ O ₃ x (20 to 80) SiO ₂ . The crystallizates have an X-ray diffraction pattern typical of ZSM-5 zeolites, which has at least the characteristic lattice plane distances listed in Table 1. Furthermore, the dehydrated crystals at 600 ^° C. show an IR spectrum typical for ZSM-5 zeolites which contains at least the characteristic absorption bands listed in Table 2.

Table 1: Values of the characteristic X-ray diffraction lines of the crystallizate

Actuation level distance relative intensity

1.12 ± 0.025 st

1,00 + 0,025 st

0.386 + 0.007 sst

0,382 + 0,006 st

0,376 £ 0.005 st

0.373 + 0.005 st

0.366 + 0.005 m

m · β medium, strong, very strong

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dragonfly 2% values of the characteristic IR absorption bands of the crystallizate

Absorption band relative intensity

440 +3 .st

520 + 3. st '

780 + 3 i »

1080 + 3 sst

1220 +4 sst

1630 + 5 m

3440 +6 st

3650 ± 7 m

 medium, strong, sat very strong

The ZSM-5 zeolites prepared by the process according to the invention may be modified for use, for example, in catalysts or adsorbents by the ion exchange, impregnation and / or deformation techniques known in the art.

Exercise games

example 1

A reaction mixture is prepared by mixing 7.65 g of aqueous sodium aluminate solution (about 20 % by weight AlgOo), 168 g of water and 36 g of sodium hydroxide, to which 143 _S 1 g of aqueous silica sol (about 31 × 5 Ma.-SS SiO ₂ ) is added. The synthesis mixture has a composition expressed in moles of the oxides of 5 Ha ₂ O ^»A ^ 2 ° 3 * ^ * ^ · ^Ο 2 • 1000 H ₂ O.

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The reaction mixture is placed in a polytetrafluoroethylene-lined autoclave and crystallized at 175 ⁰ G under a temperature / pressure ratio of 0.45 K / kPa for 33 h. Thereafter, the crystals are filtered off, washed with water and dried at 120 ⁰ C.

The chemical analysis of the product dehydrated at 600 ^° C. gives a composition expressed in moles of oxides of 1.08 Ha ₂ O.Al ₂ O ₃ .34.5 SiO ₂ . The Röntg enbeugungsdiagramm the crystals is indicated in Table 1 and 3 lletaebenenabstände "The IR spectrum of the dehydrated at 600 ⁰ G crystalysate contains listed in Table 2 IR Absoiptions" bound ·.

Table 35 X-ray diffraction line values of the crystallizate ITleplane distance / "" nnr_7 relative intensity ε "% _ J

1,112 31

1,000 34

0,980 12

0.601 15

0.587 11

0,557 10

0.488 12

0.437 13

0.3861 100

0.3834 62

0.3742 43

0.3713 41

0,3658 25

0.346 15

0,342 15

0.303 15

0.297 10

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The crystallizate, after thermal activation for 3 to 4 hours at 600 ^° C., has a water-vapor adsorption capacity of 3.78 Ua.% At room temperature and a partial vapor pressure of O ₈ 080 kPa and a gastric vapor adsorption capacity of 7.95 Ma at room temperature and a benzene partial pressure of 2.40 kPa

Example 2

A reaction mixture according to Example 1 is prepared and aged for 4 hours at room temperature before crystallization. After a crystallization time of 24 h at 175 ⁰ C the crystallized product shows the X-ray shown in Table 1 and 2 respectively · IR values and a Wasserdampfadsorptionskapazität of 3.65 Ha »-% and a Benzendampfadsorptionskapazitat of 8.12 Ma _e ~%.

Example .. ^.

A reaction mixture according to Example 1 is prepared and aged for 20 hours at room temperature before crystallization. After a crystallization time of 22 h at 175 ^° C., the crystals show the X-ray or IR values given in Tables 1 and 2 and a water vapor adsorption capacity of 3.71 Mb% and a gas vapor vapor adsorption capacity of 8.08% by weight. ,

Example 4

A reaction mixture is prepared analogously to Example 1 from 7.65 g of aqueous sodium aluminate solution, 168 g of water, 8.60 g of sodium hydroxide and 286.2 g of aqueous silica sol (composition of the reaction mixture: 10 Ua ₂ O.Al ₂ O., x 100 SiO ₂ · 136O H ₂ O), aged for 8 hours at room temperature and then 90 h crystallized at 150 ⁰ C, "the crystals shows the X-ray shown in Table 1 and 2 or * IR values and a Wasserdampfadsorptionskapazität of 3» 95 «$ and a gastric vapor adsorption capacity of 7.86

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Example 5

It is a reaction mixture as in example 1 from 7.65 g of aqueous Hatriumaluminatlösung _s 1000 g of water, 35 »5 g Hatriutahydroxid and 429.3 g of aqueous silica sol prepared (composition of the reaction mixture! 33 Na ₂ O · Al ₂ O, SiO ₂ β 150 4800 HgO) for 8 h at room temperature and then crystallized at 200 ^° C. for 12 h. The crystals show the XRF and IR values given in Tables 1 and 2, and a water vapor adsorption capacity of 3 _s 6O Ma _e -% and a benzene vapor adsorption capacity of 7 "65 Ha" - $ S.

Example 6

It is a reaction mixture, analogously to Example 1 from 7.65 g of aqueous Itfatriumaluminatlösung, 168 g of water, 3.08 g of sodium hydroxide, 0.28 g of calcium hydroxide and 143.1 g of aq. Silica prepared (composition of the reaction mixture: 4.76 Na ₂ O · 0.25 CaO · Al ₂ O ₃ · 50 SiO ₂ · 1000 HpO), aged at room temperature for 8 h and then crystallized at 175 ⁰ C for 36 h. The crystals show the X-ray or IR values given in Tables 1 and 2 and a hydrogen vapor adsorption capacity of 3.85 Ma. % and a vapor vapor adsorption capacity of 7.97% by mass.

Claims (1)

^4C 237 60 2 3 invention claim A process for the preparation of high-silica zeolites of the type ZSM-5, wherein an aqueous reaction mixture at elevated temperature and pressure is maintained a time necessary for the crystallization of the siliceous ZSM-5 zeolites, characterized in that the agitated or quiescent reaction mixture except one source for alkali and / or alkaline earth metal oxide, a source of alumina, a source of silica and water contains no further additives. Method according to item 1, characterized in that a moving or quiescent reaction mixture of the composition, expressed in moles of oxides, of (3 to 20) M _{2 / n} 0. Al ₃ O ₃ (15 to 150) SiO ₂ · (500 to 5000) H ₀ O at a temperature of from 6 to 200 h C. 80 to 200 ⁰ C is crystallized under increased pressure. 3. The method according to the items 1 and 2, gekenn ze zeie ie -et · in that the crystallization of the reaction mixture after 4 to 20 hours aging of the reaction mixture is carried out at room temperature.