DE2058871B2 - Process for producing a zeolite - Google Patents

Description

in which θ means the Bragg angle, SST "very strong", ST "strong", M "medium" and SCH "weak".

The access of molecules to the zeolite which can be prepared according to the invention is through its openings which are about 5 Å in diameter. The zeolite that can be produced according to the invention is hereinafter referred to as "Zeolite KSO1".

With regard to e.g. B. the analysis of the structure of the X-ray diffraction methods used according to the invention that can be prepared zeolite or the corresponding The apparatus, the moisture content, the temperature and the orientation of the powder crystals can change the The intensity and position of the X-ray reflection lines vary to a certain extent. Through the above X-ray diffraction spectrum given to elucidate the structure of the zeolite KSOL which can be prepared according to the invention therefore, such materials should not be excluded that are due to one of the aforementioned Variables or in some other known way a slight change in terms of intensity or show a shift in the position of one or more of the X-ray reflection lines listed in Table A.

The full X-ray diffraction diagram of a Typical example of a zeolite KSOt is shown in Table B, with a Cu-K «i radiation of one wavelength of 1.5405 A was used.

Table B.

rf, A

Relative
Intensity,
(100 · M ₀ )

description
of the reflection lines

7.55 11.7 50 B. 9.30 9.5 26th B ₁ D 12.90 6.86 69 S. 16.00 5.53 48 EB, D 17.75 4.99 100 *) S. 19.90 4.45 46 S. 21.00 4.23 250 SB 22.45 3.96 42 S. 26.00 3.42 62 S. 28.00 3.18 88 EB ₁ D 30.20 2.96 S. 30.40 2.94 A CA SB, D 30.65 2.91 D. 31.60 2.83 S. 34.60 2.59 36 S. 38.30 2.35 2 S. 39.20 2.30 4th S. 39.40 2.29 4th S. 42.70 2.12 6th S. 43.50 2.08 31 S. 47.80 1.90 11 S. 50.65 1.80 43 S. 53.40 1.71 31 S. 54.35 1.69 8th S. 54.98 1.67 16 S. 56.00 1.64 13th B. 61.40 1.51 11 B.

*) / ₀ = intensity of the strongest reflection line that appears separately in the diagram.

The letters used to describe the reflection lines in Table B are as follows Meaning:

S = sharp, D = diffuse, B = wide, SB = very wide, EB = extremely wide; θ = Bragg angle, d = distance between the lattice planes.

The zeolite KSOL which can be produced according to the invention also has a very special one and it is different from others Adsorption behavior differentiating between zeolite types and η-hexane and 2,3-dimethylbutane. After Dehydration carried out at 240 ° C and under reduced pressure is that at 100 ° C and one

ίο Hydrocarbon pressure of 40 Torr measured adsorption of η-hexane at least 0.25 mmoles / g and the ratio of the value mmoles of adsorbed n-hexane / g 2,3-dimethylbutane adsorbed to the value of mmol / g at least 8: 1.

With regard to the proportion of η-hexane adsorbed by the zeolite KSOl, which in the aforementioned Conditions is at least 0.25 mmol / g, it should be noted that depending on the applied Special production conditions also zeolites KSOl can be obtained, which a considerable have a higher ability to adsorb n-hexane, for example an adsorption value of at least 0.40 mmol / g or even at least 0.75 mmol / g. If a zeolite KSOL is used, then often a material is preferred whose ability to adsorb η-hexane is as high as possible.

In the context of the process according to the invention, it is important to start from a cogel and in addition, constantly stirring or shaking during production.

The term "cogel" as used herein refers to a hydrogel produced by precipitating an aluminum hydroxide gel onto a silicon dioxide hydrogel obtained silica / alumina mixture. Such a cogel is therefore not a "joint precipitation" since it is used to produce a such joint precipitation of silica hydrogel and aluminum hydroxide gel is at least approximate precipitated out of solution at the same time. It is believed that the silica spheres are in the cogel are coated with an aluminum oxide layer.

_{With regard to the SiO 2} ZAl ₂ O ₃ molar ratio required in the starting mixture, this ratio in the amorphous silicon dioxide / aluminum oxide cogel should be 9.8: 1 to 12: 1.

A silica / alumina cogel can expediently by precipitating an aluminum hydroxide gel on a silicon dioxide hydrogel in an aqueous one Medium can be produced by adding an aluminum compound and an alkaline reacting solution

so clogs. A very useful method of making a silica / alumina cogel is in that one first consists of an aqueous solution containing silicate ions by adding mineral acid a silica hydrogel precipitates, then an aluminum salt is added to the solution and finally causes the aluminum hydroxide gel to precipitate by adding an alkaline solution. as Aqueous solution containing silicate ions can serve as water glass. The mineral acid is preferably that Acid from which the aluminum salt to be added is derived. Water soluble aluminum salts are preferred. A very suitable solution with an alkaline reaction is aqueous ammonia. It is Sometimes it is advisable to use the silicon dioxide hydrogel obtained before the actual production of the cogel first for some time either at room temperature or at elevated temperatures such as temperatures from 25 to 40 ° C, to age. After the formation of the

Cogel is separated the resulting precipitate from the liquid, washed with water and dried at at least 100 ⁰ C. The production of a Cogel suitable as a starting material for the production of the zeolite KSOL according to the invention is explained in greater detail in British patent specification 11 81 188.

Instead of a cogel obtained by the method described above, a large amount of Advantage a commercially available silica / alumina cracking catalyst with a low aluminum oxide content can be used as a cogel. Such cracking catalysts generally have an alumina content of about 10 to 16 percent by weight and are also obtained in the form of a cogel. Using such commercially available silica / alumina cracking catalysts Excellent results are obtained as the starting material for the production of the zeolite KSOL according to the invention achieved.

The production of the zeolite KSOL according to the Cogel process can be carried out both at atmospheric pressure and at elevated pressures. If higher reaction temperatures are used than the boiling point of the mixture, the process is preferably carried out in an autoclave at autogenous pressure. The zeolite KSOl is preferably prepared by adding the mixture, for. B. holds ^{at temperatures of 90 to HO 0} C for at least 4 hours with stirring or shaking. In order to ensure that a high yield of crystalline product is obtained, it is important that the mixture from which the zeolite is prepared is kept in motion during the recovery of the zeolite KSOL by the Cogel process. After the formation of the zeolite, the crystals are separated from the mother liquor, for example by filtering, decanting or centrifuging. The crystal mass is then washed with water and dried at temperatures of 100 to 200 ⁰ C.

The zeolite KSOL is very suitable as a catalyst or catalyst carriers for a wide variety of catalytic processes. In terms of its uniform The zeolite KSOl is of particular importance for selective methods for pore diameter Carrying out catalytic processes in which due to the fact that only compounds with linear Structure can penetrate into the zeolite or leave it from a mixture of compounds with linear and compounds with a branched structure only those with a linear structure can be converted or only compounds with a linear structure are formed. Examples of such catalytic processes are selective (hydro) cracking and dehydration of n-paraffin hydrocarbons, selective hydrogenation, Hydration and amination of unbranched alkenes and the selective dehydration of unbranched alkenes Alcohols in mixtures, which the compounds together with corresponding compounds with a branched and / or cyclic structure.

If desired, the exchangeable sodium ions of the zeolite KSOl before the practical Use can also be replaced by other cations. If by ion exchange a ΝΗί-zeolite has been obtained, it can be converted into the H + form of the zeolite by calcination.

The zeolite KSOL is not only suitable as a catalyst or as a catalyst carrier but can can also be used for numerous other purposes, for example as adsorption, extraction or Desiccant or ion exchanger.

In addition to the use of the zeolite KSOL as a carrier for catalysts for the conversion of hydrocarbons, an important application of this zeolite is its use as a molecular sieve for the separation of compounds with an unbranched structure from a mixture of these compounds with corresponding compounds with a branched structure. For this purpose, the zeolite should be at least partially dehydrated. Both the zeolite KSOL as such and the product made from it by replacing at least some of the sodium ions with other cations are suitable for the aforementioned application.
The examples illustrate the invention.

example 1

A commercially available silicon dioxide / aluminum oxide cracking catalyst with a water content of 23.8 percent by weight, an aluminum oxide content of 13.1 percent by weight (based on the dry material), a sodium content of below 1 percent by weight (based on on the dry material) and a specific surface area or a pore volume after calcination at 600 ° C. of 668 m ² / g and 0.69 cm ³ / g, respectively.
It becomes a mixture of the molar composition

4 Na ₂ O · Al ₂ O ₃ · 11.2 SiO ₂ · 150 H ₂ O

prepared by gradually introducing a solution of 32 g of sodium hydroxide in 75 ml of water, with stirring, into a mixture of 102.2 g of the aforementioned cracking catalyst and 163.5 ml of water. The total mixture is then refluxed with stirring and reflux for 12 hours. After cooling the reaction mixture, the zeolite is filtered, washed with water as long until the filtrate has a pH below 10, and finally dried at 120 ⁰ C.

The zeolite KSOl (zeolite I) obtained in this way has the following properties:
Powder X-ray diffraction pattern: essentially as shown in Table B.

Chemical composition:

1.05 Na ₂ O • Al ₂ O ₃ • 4.85 SiO ₂ • 5.15 H ₂ O;

Adsorption at 100 ° C and a hydrocarbon pressure of 40 Torr (after dehydration at 240 ⁰ C and under reduced pressure): adsorption of n-hexane = 0.8 mmol / g; Adsorption of 2,3-dimethylbutane = 0.055 mmol / g.

mmol adsorbed n-hexane / g

mmol 2,3-dimethylbutane adsorbed / g

= 14.5

The specific surface area and the pore volume amount after drying at 225 ⁰ C 42 MVG and 0.13 cmVg.

Example 2

As a starting material for the production of a zeolite KSOL, a commercially available one becomes Silica / alumina cracking catalyst with a water content of 15.3 weight percent, a Aluminum oxide content or sodium content (based on the dry material) of 12.8 or below 0.5

Percentage by weight and a specific surface area or a pore volume after calcination at 600 ° C. of 658 m ² / g and 0.75 cm ³ / g, respectively.
It becomes a mixture of the molar composition

4 Na ₂ O · Al ₂ O ₃ ■ 11.2 SiO ₂ · 150 H ₂ O

prepared by adding a solution of 8 kg of sodium hydroxide in 18.75 liters of water with stirring in a A mixture of 24.82 kg of the aforementioned cracking catalyst and 41.6 liters of water is introduced. The overall mix ι ο is stirred and refluxed for 12 hours boiled. After the reaction mixture has cooled down, the zeolite is filtered off, so long with water washed until the pH of the filtrate is below 10 and finally dried at 120.degree.

The zeolite KSOl (zeolite H) produced in this way has the following properties:

Powder X-ray diffraction pattern: essentially as shown in Table B.

Chemical composition:

1.12 Na ₂ O • Al ₂ O ₃ • 5.03 SiO ₂ • 4.70 H ₂ O

Adsorption at 100 ⁰ C and a hydrocarbon pressure of 40 Torr (after dehydration at 24O ⁰ C and reduced pressure): adsorption of n-hexane = 0.84 mmol / g; Adsorption of 2,3-dimethylbutane = 0.06 mmol / g.

mmol adsorbed n-hexane / g
mmol 2,3-dimethylbutane adsorbed / g

= 14.0

The specific surface area and the pore volume after drying at 225 ° C. are 286 m ² / g and 0.24 cm ³ / g, respectively.

Comparative example

The experiment from Example 1 is repeated, but the total mixture is heated ^{to 100 ° C. in a closed vessel for 24 hours without stirring.}

The X-ray diffraction analysis shows that the product made in this way is entirely amorphous Substance exists.

A comparison of the result of Example 1 with that of the comparative example shows that it is in the Production of the zeolite KSOl by the Cogel process is important that the mixture during the Process is constantly stirred.

Claims (1)

Claim: Process for making a zeolite having the empirical formula 0.7-1.2Na ₂ O · Al ₂ O ₃ · 4.7-5.3SiO ₂ · xH ₂ O, where χ has a maximum value of 12, preferably 3 to 9 and a powder X-ray diffraction diagram with the reflection lines shown in Table A by heating an aqueous, alkaline mixture of an aluminum compound and a silicon compound at elevated temperatures, then separating the crystalline zeolite formed, washing and Drying, characterized in that an aqueous mixture of sodium hydroxide and a cogel of aluminum hydroxide on silica hydrogel with a composition expressed in moles of the oxides 3.8-4.2Na ₂ O · Al ₂ O ₃ · 9.8-12.0SiO ₂ ·
125-375H ₂ O heated with stirring or shaking at temperatures of 70 to 160 ⁰ C, which comprises separating the crystals of the zeolite formed by the mother liquor, washed and dried at temperatures of 100 to 200 ° C. The invention relates to a method for producing a zeolite with certain, particularly advantageous Adsorption properties. The term "zeolite" generally refers to a class of naturally occurring, hydrated water Metal aluminosilicates with a crystalline structure. However, there have already been numerous zeolites as well synthetically produced. The zeolites differ from one another in terms of their crystal structure and composition and adsorption properties. Their respective special structure can be determined by means of the Determine powder x-ray diffraction analysis. The zeolites are made up of a three-dimensional lattice of S1O4 and AKV tetrahedra, which share common Oxygen atoms are in connection with each other, built up. The negative electron valence of aluminum containing tetrahedron is created by the incorporation of cations, such as alkali or alkaline earth ions, in the Crystal compensated. These cations can be exchanged for other cations by suitable exchange processes be replaced. The zeolites are therefore often used as ion exchangers. Due to this structure, the zeolite crystals have cavities of molecular dimensions, which are usually filled with water of hydration. After at least partial dehydration, these can Zeolites are used as effective adsorbents, with the adsorbed molecules in the aforementioned cavities are retained. The cavities are located about in the crystal structure openings accessible. The dimensions and the are dependent on the cross-sectional area of these openings The shape of the molecules that can be adsorbed is limited. This makes it possible to identify certain molecules separated from mixtures on the basis of the dimensions of these molecules by only very specific JO 35 40 45 50 55 bO 65 molecules are adsorbed by the zeolite. With reference to this property, many zeolites are therefore referred to as "molecular sieves". This property of the zeolites is exploited in particular when the zeolites are used as catalysts or catalyst supports in processes in which only those are converted from a mixture of different compounds whose molecules have the appropriate shape and dimensions to penetrate the molecular sieve. The object of the invention was to provide a process for the production of a new zeolite of the molecular sieve type with certain adsorption properties available, which is called adsorption, Extracting or drying agents or as ion exchangers and above all as a catalyst or catalyst carrier, particularly suitable for the catalytic conversion of hydrocarbons The process of the present invention for making a zeolite having the empirical formula 0.7-1.2 Na ₂ O Al ₂ O ₃ 4.7-53 SiO ₂ ■ xH ₂ O, where χ is at most 12, preferably 3 to 9, and a powder X-ray diffraction diagram with the reflection lines shown in Table A. Heating an aqueous, alkaline mixture of an aluminum compound and a silicon compound at elevated temperatures, subsequent separation of the crystalline zeolite formed, washing and drying, is characterized in that an aqueous mixture of sodium hydroxide and a cogel of aluminum hydroxide on silica hydrogel one expressed in moles of the oxides composition 3.8-4.2 Na ₂ O · Al ₂ O ₃ · ₂ · 9,8-12,0SiO 125-375 H ₂ O heated with stirring or shaking to temperatures of 70 to 160 ° C that the crystals of the formed Separates zeolite from the mother liquor, washed and dried at temperatures of 100 to 200 ° C This new type of zeolite is different from other representatives of the zeolites by the specific powder X-ray diffraction diagram differed, the relative intensities of which are compiled in Table A below are, Table A. Wavelength = 1.5405 Å COT Radiation = Cu-K «1 relative intensity ' YY 1 20th M. 7.15-7.95 NS M. 8.80- 9.80 ST i 12.70-13.10 M ^; 15.00-17.00 SST; 17.55-17.95 M \ 19.60-20.20 SST: 20.40-21.60 M \ 22.15-22.75 ST 5 25.80-26.20 SST i; 27.20-28.80 ti 29.90-30.50] 30.00-30.80 I. 30.25-31.05 I. 31.30-31.90 yrs 34.40-34.80 50.35-50.95