WO2011095140A1

WO2011095140A1 - Method of manufacture of zeolites with pentasil structure with controlled distribution of aluminium atoms in the skeleton

Info

Publication number: WO2011095140A1
Application number: PCT/CZ2010/000113
Authority: WO
Inventors: Oleg Bortnovsky; Věnceslava TOKAROVÁ; Blanka WICHTERLOVÁ; Jiří DĚDEČEK; Zdeněk SOBALÍK; Olga Gonsiorová; Vendula BALGOVÁ
Original assignee: Výzkumný Ústav Anorganické Chemie; Ústav Fyzikální Chemie J. Heyrovského Av Čr
Priority date: 2010-02-05
Filing date: 2010-11-04
Publication date: 2011-08-11
Also published as: CZ201091A3; CZ301937B6

Abstract

The invention relates to a method of manufacture of microporous zeolites with pentasil structure with controlled distribution of aluminium atoms in an alumino-silicate tetrahedrally coordinated skeleton in "A1 pairs" in (A1-O-(Si-O)_n=1,2-A1) sequences localized in a single ring and in different rings in A1-O-(Si-O)_n>2-A1 sequences. Different distribution of Al atoms in alumino-silicate skeleton is achieved by hydrothermal synthesis using a suitable combination of sources of silicon and aluminium, utilizing their different reactivity, presence of alkaline metal salts, and the use of silicate or alumino-silicate amorphous nano-dimensioned precursors with controlled reactivity, seeding crystals and different times of ageing of the reaction mixture. Skeleton of zeolites with pentasil structure with a molar ratio of Si : A1 = 8 : 1 to 40 : 1 contains 5 to 85 % aluminium atoms in the form of A1 pairs and 15 to 95 % of aluminium atoms in the form of isolated A1 atoms. ˙

Description

Method of manufacture of zeolites with pentasil structure with controlled distribution of aluminium atoms in the skeleton

Technical Field

The invention is related to a method of manufacture of zeolites with pentasil structure with controlled distribution of aluminium atoms in the skeleton.

Background Art

Zeolites are crystalline alumino-silicates where the coordination of trivalent aluminium in the tetrahedrally coordinated silicate skeleton leads to a negative charge of the skeleton. In the synthesized zeolites, this negative charge is compensated by organic bases, protons, ammonium cations, or the cations of alkaline metals or alkaline earths.

BEA, MFI and FER zeolites, belonging to the group of zeolites with pentasil structure, exhibit a low Al concentration in the skeleton (molar ratio of Si : Al > 8 : 1, usually Si : Al > 12 : 1) and form pores with a size of approx. 5.3 to 6.6 A (Baerlocher, Ch.; Meier, W. M.; Olson, D. H.: Atlas of Zeolite Framework Types, 5th Ed. Elsevier, 2001), corresponding to the size of organic molecules. The molecular sieve effect derived from this fact is utilized in shape selectivity of zeolites in the synthesis and transformation of organic substances and in separation processes. Synthesis of zeolites with BEA, MFI and FER structures is directed towards controlling the size of crystallites, especially crystallites with dimensions of less than 1 μιη down to the dimensions of nanocrystals (Kuechl, D. E.; Benin, A. I.; Knight, L. M.; Abrevaya, H.; Wilson, S. T.; Sinkler, W.; Mezza, T. M.; Willis, R. R.: Microp. Mesop. Mater. 127 (2010) 104 and patents US 6951638, US 5672331, ES 21241420), preferentially using gel precursors (CZ 299372), that permit easy transport of reactants in catalytic and separation processes. In addition, patent US 6524984 describes the preparation of zeolitic crystals on the surface of silicon microspheres and the preparation of crystals not containing aluminium atoms of the skeleton on the surface and the derived surface proton and cation active centres. Patents EP 055356 and US 5200168 describe dealumination of the zeolite skeleton by hydrothermal treatment and acidic or complexing agents. Patents US 5763347, US 5110478 and JP 2000026115 describe methods of synthesis of zeolites enabling the growth of zeolitic crystalites on solid supports and in the form of films for their application in membrane reactors. Synthesis of zeolites with pentasil BEA, MFI and FER structures is performed under hydrothermal conditions in alkaline medium at pH approx. 10, generally in the presence of ammonium organic bases as templates, in the case of zeolites with MFI structure with a molar ratio of Si : Al < 30 : 1, preferentially in the presence ethanol or isopropanol and ammonia, and FER structures in the absence of an organic template, see patent US 4650654.

Patent GB 1567948 describes synthesis of zeolites with MFI structure using seed crystals with pentasil structure. Patents WO 2006087337 and EP 1707533 describe the preparation of highly reactive silicate or alumino-silicate gels and their advantageous use as sources of Si and Al for accelerating crystallization in the hydrothermal synthesis of zeolites with BEA or MFI structure. The procedure pursuant to patent CZ 299372 uses these gels for synthesis of zeolite crystals with MFI structure with controlled particle size in the range 100 to 200 mm. However, none of these four procedures is concerned with the controlled distribution of aluminium atoms in the zeolite skeleton.

Patent RU 2174952 is concerned with synthesis of zeolites with the MFI structure with uniform chemical composition in the zeolite crystal, i.e. homogeneous distribution of Al atoms along the crystal axis. This synthesis has the disadvantage that it does not deal with the distribution of Al atoms in the zeolite skeleton.

However, none of the above patents is concerned with targeted synthesis of zeolites with different distributions of Al atoms in the skeleton. It has been demonstrated for zeolites with MFI structure that the distribution of aluminium atoms in the skeleton is not random, not governed by statistical rules, but is controlled by the kinetic or energy parameters of their synthesis (Dedecek, J.; Kaucky, D.; Wichterlova, B.: Chem. Commun. (2001) 970 and Dedecek, J.; Kaucky, D.; Wichterlova, B., Gonsiorova O.: Phys. Chem. Chem. Phys. 4 (2001) 5406). This fact anticipates the potential for controlled distribution of Al in the skeleton of zeolites with pentasil structure during their preparation.

The distribution of aluminium atoms in the alumino-silicate skeleton here refers to the concentration of "Al pairs" (i.e. Al-0-(Si-0)i_j2-Al sequences in one skeletal ring) and the concentration of "isolated Al atoms" located in different rings in Al-0-(Si-0)„>2-Al sequences (Dedecek, J.; Kaucky, D.; Wichterlova, B., Gonsiorova O.: Phys. Chem. Chem. Phys. 4 (2001) 5406). It is important that this corresponds to the distribution of aluminium atoms in the skeletal T positions, but not to the distribution of aluminium atoms between skeletal and extra-skeletal positions, such as, for example, in dealuminated zeolites, and similarly also not to a change in the spatial concentration of aluminium, as generally occurs in large crystals.

The value of the Si : Al ratio in the skeleton of zeolites with pentasil BEA, MFI and FER structures is determined from quantitative analysis of the ²⁹Si and ²⁷ Al MAS NMR spectra of the zeolites. The Al-O-Si-O-Al sequence in the skeleton, determined from quantitative analysis of the Si(2Si2Al) atoms from the Si MAS NMR spectra, practically does not occur in pentasil structures (generally < 3 % Al). The concentration of Al-0-(Si-0)2-Al sequences in the skeleton (Al pairs) is determined from the intensities of the d-d bands in the Vis spectra of Co(II)-zeolites (with maximum degree of exchange of Co(II) ions in the cation positions) dehydrated at a temperature of 450 °C for a period of 3 hours and the corresponding absorption coefficients for the cation positions of the Co(II) ions in the zeolitic pentasil BEA, MFI and FER structures (Dedecek, J; Capek, L; Kaucky, D.; Wichterlova B.: J. Catal. 211 (2002) 198, and Dedecek, J.; Kaucky, D.; Wichterlova, B.: Microp. Mesop. Mater. 35-36 (2000) 483 and Kaucky, D.; Dedecek, J.; Wichterlova, B.: Microp. Mesop. Mater. 31 (1999) 75, resp.). The concentration of isolated Al atoms (Al-0-(Si-0)_n>₂-Al) corresponds to the difference in the Al concentration in the skeleton and the concentration of Al atoms in Al pairs.

The H-forms of zeolites with BEA, MFI and FER pentasil structures are highly active selective catalysts for acid-catalyzed reactions for the conversion of methanol to olefins and aromates (EP 0114498 a EP 0150740), alkylation of benzene or toluene by olefins to alkyl benzenes or alkyl toluenes (CA 2106028, EP 0160335, WO 2006060158), isomerization and cracking of paraffins (US 5095168, IT 1240646) utilizing the high acidity of their protons and shape-selective pores. Interesting redox properties compared to the metal oxide particles on amorphous inorganic carriers are exhibited by the ion-exchange cations of transition metals (Cu, Co, Fe) and their oxo-cationic complexes in BEA, MFI and FER zeolites with pentasil structures, especially in reactions of selective reduction of NO_x in an oxidation atmosphere by ammonia or hydrocarbons (WO 0241991, US 2007248517, EP 1754527, EP1973633), the decomposition of N₂0 to its molecular components (US 5171553) and the oxidation of hydrocarbons by N₂0 to selective oxidation products (WO 9527691).

It has been demonstrated that the selectivity of acid-catalyzed reactions of the conversion of hydrocarbons on H-MFI zeolites is affected by the distribution of aluminium atoms in the skeleton, which controls the location and properties of the charge-compensated proton centres (Sazama, P.; Dedecek, J.; Gabova, V.; Wichterlova, B.; Spoto, G.; Bordiga, S.: J. Catal 254 (2008) 180). The distribution of Al in the skeleton or the presence of Al-pairs compensating isolated Cu(II) ions in Cu-MFI zeolites also controls the rate of the selective reduction of NO_x to N₂ by decane (Capek, L.; Dedecek, J.; Wichterlova, B.; Cider, L.; Jobson, E.; Tokarova, V.: Appl. Catal. B-Environ. 60 (2005) 147-153), an important reaction for their application in the elimination of NO_x from the exhaust gases of diesel engines. In contrast, the high activity of Co-BEA zeolites in the selective reduction of NO_x-N₂ by propane in the exhausts from gas power plants with high water contents is caused by the presence of Co-oxo particles charge- compensated by isolated Al atoms in the skeleton (Capek, L.; Sazama, P.; Dedecek, J.; Wichterlova, B.: J. Catal., 2010, in press).

The disadvantages of earlier methods of synthesis of BEA, MFI and FER zeolites with pentasil structures is that they do not permit control of the distribution of aluminium between Al-pairs and isolated Al atoms in the zeolite skeleton.

The above-mentioned drawbacks are at least partly eliminated by the methods of manufacturing zeolites with pentasil BEA, MFI and FER structures with controlled distribution of aluminium atoms in the skeleton according to the invention.

Disclosure of Invention

1. A method of manufacture of zeolites with pentasil structure with controlled distribution of aluminium atoms in the skeleton consisting in that the source of at least one substance selected from the group including aluminium and silicon is mixed at least with an aqueous solution of at least one substance taken from the group including sodium hydroxide, potassium hydroxide, sodium aluminate, ethanol, ammonia, a quaternary ammonium organic template, which is at least one of the substances selected from the group including tetraethyl ammonium bromide, tetrapropyl ammonium bromide and tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide, where the molecular ratios in the reaction mixture are Si : Al = 7.5 : 1 to 90 : 1 and H₂0 : Si0₂ = 5 : 1 to 50 : 1, the reaction mixture is left to age at laboratory temperature with mixing for a period of at least 10 minutes and is then left to crystallize under hydrothermal conditions at a temperature of 130 to 170 °C for a period of at least 15 hours, where the skeleton of the zeolite formed contains Si and Al in a molar ratio of Si : Al = 8 : 1 to 40 : 1, characterized by the fact that the kinetics of synthesis of the zeolite are controlled by the selection of the source of at least one of the substances selected from the group including aluminium and silicon, where this source is selected particularly from the group including sources with a specific surface area of 600 to 1000 m²/g and degree of cross- linking of 15 to 90 %, where the skeleton of the zeolite formed contains 5 to 85 % aluminium atoms in the form of Al pairs and 15 to 95 % of the aluminium atoms in the form of isolated Al atoms.

2. The method of manufacture according to paragraph 1, characterized by the fact that first an amorphous precursor is prepared with a specific surface area of 600 to 800 m²/g and degree of cross-linking of 70 to 90 % in that, at pH 7.5 to 8, an aqueous solution of sodium silicate containing 10 to 20 % wt. Si0₂ and 2.9 to 5.9 % wt. Na₂0 is precipitated by an aqueous solution containing at least one substance selected from the group including aluminium sulphate and aluminium nitrate with a total content of 1 to 5 % wt. A1₂0₃, 10 to 40 % wt. H₂S0₄ and 10 to 40 % wt. HN0₃, and then the liquid phase is separated from the precipitated precursor.

3. The method of manufacture according to paragraph 1, characterized by the fact that first an amorphous precursor is prepared with a specific surface area of 700 to 1000 m²/g and degree of cross-linking of 15 to 30 % in that an aqueous solution of a sol of silicic acid containing 10 to 40 % wt. Si0₂ is precipitated by an aqueous solution containing at least one substance selected from the group including aluminium nitrate with a content of 0.5 to 2 % wt. A1₂0₃, polyaluminium chloride containing up to 20 % wt. A1₂0₃ and 2.5 to 5 % wt. HN0₃, and then the liquid phase is separated from the precipitated precursor.

4. The method of manufacture according to paragraph 1, characterized by the fact that the source of the silicon, which is a sol of silicic acid, is mixed with an aqueous solution containing sodium aluminate, sodium hydroxide and a mixture of template, containing an aqueous solution of ammonium hydroxide and tetramethyl ammonium bromide, and with seeding crystals of zeolite with structure BEA in an amount of up to 10 % wt. in relation to the sum of the contents of Si0₂ and A1₂0₃ in the reaction mixture, where the molar ratios in the reaction mixture are Si : Al = 12 : 1 to 25 : 1, tetraethyl ammonium bromide : Si = 0.2 : 1 to 0.5 : 1, Na : Si = 0.05 : 1 to 0.3 : 1 and Ν¾ΟΗ : Si = 0.5 : 1 to 2 : 1, the reaction mixture is left to age and is then crystallized at a temperature of 130 to 150 °C for a period of at least 5 days, where the skeleton of the formed zeolite with BEA structure with molecular ratio Si : Al = 12 : 1 to 25 : 1 contains 40 to 95 % of the aluminium atoms in the form of isolated Al atoms. 5. The method of manufacture according to paragraph 2, characterized by the fact that the source of silicon and aluminium, consisting in the amorphous precursor with a molar ratio of Si : Al = 12 : 1 to 20 : 1 washed with an ammonium nitrate solution with a concentration of

0.5 mol/1 is mixed with an aqueous solution containing tetraethyl ammonium hydroxide and with seeding crystals of zeolite with BE A structure in an amount of up to 10 % wt. in relation to the sum of the contents of Si0₂ and A1₂0₃ in the reaction mixture, where the molar ratios in the reaction mixture are tetraethyl ammonium bromide : Si0₂ = 0.1 : 1 to 1 : 1 and H₂0 : Si0₂ = 5 : 1 to 20 : 1 , the reaction mixture is left to age and then to crystallize at a temperature of 130 to 150 °C for a period of 2 to 5 days, where the skeleton of the formed zeolite with BE A structure with molar ratio Si : Al = 12 : 1 to 20 : 1 contains 30 to 65 % aluminium atoms in the form of Al pairs.

6. The method of manufacture according to paragraph 1, characterized by the fact that the source of silicon and aluminium is a substance prepared by the reaction of sodium sulphate with stirring for a period of at least 60 minutes at laboratory temperature with a solution of at least one substance selected from the group including aluminium nitrate and aluminium chloride, and with an aqueous solution containing tetrapropyl ammonium hydroxide, where the molar ratios in the reaction mixture are Si : Al = 20 : 1 to 90 : 1 , tetrapropyl ammonium hydroxide : Si0₂ = 0.3 : 1 to 0.6 : 1, OH : Si = 0.3 : 1 to 0.6 : 1 and H₂0 : Si0₂ = 20 : 1 to 30 :

1 , the reaction mixture is left to age with stirring for a period of at least 60 minutes and then to crystallize at a temperature of 150 to 170 °C for a period of at least 3 days, where the skeleton of the formed zeolite with MFI structure with a molar ratio of Si : Al = 12 : 1 to 40 : 1 contains 80 to 95 % aluminium atoms in the form of isolated Al atoms.

7. The method of manufacture according to paragraph 1, characterized by the fact that the source of silicon and aluminium is a substance prepared by the reaction of tetraethyl orthosilicate dissolved in ethanol with stirring for a period of at least 60 minutes at laboratory temperature with at least one substance selected from the group including aluminium-tri-sec- butoxide and aluminium nitrate, and with an aqueous solution containing tetrapropyl ammonium hydroxide, where the molar ratios in the reaction mixture are Si : Al = 20 : 1 to 90 : 1, tetrapropyl ammonium hydroxide : Si0₂ = 0.3 : 1 to 0.6 : 1, , Na₂0 : Si0₂ = 0 : 1 to 0.2 : 1, OH : Si = 0.3 : 1 to 0.4 : 1, ethanol : Si0₂ = 1 : 1 to 1.8 :1 and H₂0 : Si0₂ = 20 : 1 to 45 : 1 , the reaction mixture is left to age with stirring for a period of at least 60 minutes and then to crystallize at a temperature of 150 to 170 °C for a period of at least 3 days, where the skeleton of the formed zeolite with MFI structure with a molar ratio of Si : Al = 12 : 1 to 40 : 1 contains 80 to 95 % aluminium atoms in the form of isolated Al atoms.

8. The method of manufacture according to paragraph 1, characterized by the fact that the source of silicon and aluminium is a substance prepared by the reaction of tetraethyl orthosilicate dissolved in ethanol with stirring for a period of at least 60 minutes at laboratory temperature with at least one substance selected from the group including aluminium chloride and aluminium hydroxide, dissolved in water with the addition of sodium cations in the form of at least one substance selected from the group including NaOH and Na₃P0₄, in an amount of up to 56 mmol Na⁺ ions per 100 ml of the reaction mixture, and an aqueous solution containing tetrapropyl ammonium hydroxide, where the molar ratios in the reaction mixture are Si : Al = 7.5 : 1 to 45 : 1, tetraethyl ammonium hydroxide : Si0₂ = 0.3 : 1 to 0.6 : 1, Na₂0 : Si0₂ = 0 : 1 to 0.2 : 1, OH : Si = 0.3 : 1 to 0.4 : 1, ethanol : Si0₂ = 1 : 1 to 1.8 :1 and H₂0 : Si0₂ = 20 : 1 to 30 : 1, the reaction mixture is left to age with stirring for a period of at least 60 minutes and then to crystallize at a temperature of 140 to 160 °C for a period of at least 3 days, where the skeleton of the formed zeolite with MFI structure with a molar ratio of Si : Al = 15 : 1 to 40 : 1 contains 26 to 58 % aluminium atoms in the form of Al pairs.

9. The method of manufacture according to paragraph 3, characterized by the fact that the amorphous precursor is mixed with an aqueous solution containing at least one substance selected from a group including ethanol, ammonia, sodium hydroxide and sodium aluminate, and with seeding crystals with MFI structure in an amount of 0.2 to 2 % wt. compared to the sum of the contents of Si0₂ and A1₂0₃ in the reaction mixture, where the molar ratios of the reaction mixture are Si : Al = 12 : 1 to 20 : 1, Na₂0 : Si0₂ = 0.02 : 1 to 0.15 : 1 and N¾OH : Si0₂ = 0.2 : 1 to 1 : 1, ethanol : Si0₂ = 0.3 : 1 to 0.8 : 1, OH : Si0₂ = 0.1 : 1 to 0.3 : 1 and H₂0 : Si0₂ = 10 : 1 to 20 : 1, the reaction mixture is left to age for a period of at least 10 minutes and then to crystallize at a temperature of 150 to 170 °C for a period of 15 to 48 hours, where the skeleton of the formed zeolite with MFI structure with a molar ratio of Si : Al = 12 : 1 to 20 : 1 contains 60 to 95 % aluminium atoms in the form of isolated Al atoms.

10. The method of manufacture according to paragraph 2, characterized by the fact that the amorphous precursor is mixed with an aqueous solution containing at least one substance selected from a group including ethanol, ammonia, sodium hydroxide and sodium aluminate, and with seeding crystals with MFI structure in an amount of 0.2 to 2 % wt. compared to the sum of the contents of Si0₂ and A1₂0₃ in the reaction mixture, where the molar ratios in the reaction mixture are Si : Al = 12 : 1 to 20 : 1, Na₂0 : Si0₂ = 0.02 : 1 to 0.15 : 1 and NH4OH : Si0₂ = 0.2 : 1 to 1 : 1, ethanol : Si0₂ = 0.3 : 1 to 0.8 : 1, OH : Si0₂ = 0.1 : 1 to 0.3 : 1 and H₂0 : Si0₂ = 4 : 1 to 8 : 1, the reaction mixture is left to age with stirring for a period of at least 10 minutes and is then left to crystallize at a temperature of 150 to 170 °C for a period of 15 to 48 hours, where the skeleton of the formed zeolite with MFI structure with a molar ratio of Si : Al = 12 : 1 to 20 : 1 contains 30 to 60 % aluminium atoms in the form of Al pairs.

11. The method of manufacture according to paragraph 2, characterized by the fact that the amorphous precursor is mixed with an aqueous solution containing at least one substance selected from a group including sodium hydroxide, sodium aluminate and tetrapropyl ammonium bromide, and with seeding crystals with MFI structure in an amount of 0.2 to 2 % wt. compared to the sum of the contents of Si0₂ and A1₂0₃ in the mixture, where the molar ratios in the reaction mixture are Si : Al at least 20 : 1, Na₂0 : Si0₂ = 0.02 : 1 to 0.15 : 0.01 and tetrapropyl ammonium bromide : Si0₂ = 0.002 : 1 to 0.01 : 1, OH : Si0₂ = 0,1 : 1 to 0.3 : 1 and H₂0 : Si0₂ = 4 : 1 to 8 : 1, the reaction mixture is left to age with stirring for a period of at least 12 hours and then water is added to the reaction mixture, where the molar ratio H₂0 : Si0₂ = 20 : 1 to 30 : 1, and then the reaction mixture is left to crystallize at a temperature of 150 to 170 °C for a period of 15 to 48 hours, where the skeleton of the formed zeolite with MFI structure with a molar ratio of Si : Al = 20 : 1 to 40 : 1 contains 60 to 95 % aluminium atoms in the form of isolated Al atoms.

12. The method of manufacture according to paragraph 3, characterized by the fact that the amorphous precursor is mixed with an aqueous solution containing at least one substance selected from a group including sodium hydroxide, sodium aluminate and tetrapropyl ammonium bromide, and with seeding crystals of the zeolite with MFI structure in an amount of 0.2 to 2 % wt. compared to the sum of the contents of Si0₂ and A1₂0₃ in the mixture, where the molar ratios in the reaction mixture are Si : Al at least 20 : 1, Na₂0 : Si0₂ = 0.02 : 1 to 0.15 : 0.01, tetrapropyl ammonium bromide : Si0₂ = 0.002 : 1 to 0.01 : 1, OH : Si0₂ = 0.1 : 1 to 0.3 : 1 and H₂0 : Si0₂ = 6 : 1 to 10 : 1, the reaction mixture is left to age with stirring for a period of at least 12 hours and then water is added to the reaction mixture, where the molar ratio H₂0 : Si0₂ = 15 : 1 to 30 : 1, and then the reaction mixture is left to crystallize at a temperature of 150 to 170 °C for a period of 15 to 48 hours, where the skeleton of the formed zeolite with MFI structure with a molar ratio of Si : Al = 20 : 1 to 40 : 1 contains 30 to 50 % aluminium atoms in the form of Al pairs. 13. The method of manufacture according to paragraph 2, characterized by the fact that the amorphous precursor is mixed with an aqueous solution containing at least one substance selected from a group including sodium hydroxide and potassium hydroxide, and with seeding crystals with FER structure in an amount of 2 to 4 % wt. compared to the sum of the contents of Si0₂ and AI2O3 in the mixture, where the molar ratios in the reaction mixture are Si : Al = 8 : 1, Na : Si = 0.05 : 1 to 0.3 : 1, K : Si = 0.075 : 1 to 0.15 : 1 and H₂0 : Si = 15 : 1 to 25 : 1, the reaction mixture is left to age for a period of at least 10 minutes and then to crystallize at a temperature of 150 to 170 °C for a period of at least 2 days, where the skeleton of the formed zeolite with FER structure with a molar ratio of Si : Al = 8 : 1 to 20 : 1 contains 30 to 60 % aluminium atoms in the form of Al pairs.

14. The method of manufacture according to paragraph 3, characterized by the fact that the amorphous precursor is mixed with an aqueous solution containing at least one substance selected from a group including sodium hydroxide and potassium hydroxide, and with seeding crystals with FER structure in an amount of 2 to 4 % wt. compared to the sum of the contents of Si0₂ and A1₂0₃ in the mixture, where the molar ratios in the reaction mixture are Si : Al = 8 : 1 to 20 : 1, Na : Si = 0.05 : 1 to 0.3 : 1, K : Si - 0.075 : 1 to 0.15 : 1 and H₂0 : Si = 15 : 1 to 25 : 1, the reaction mixture is left to age for a period of at least 10 minutes and then to crystallize at a temperature of 150 to 170 °C for a period of at least 2 days, where the skeleton of the formed zeolite with FER structure with a molar ratio of Si : Al = 8 : 1 to 20 : 1 contains 40 to 85 % aluminium atoms in the form of isolated Al atoms.

The subject of the invention consists in the synthesis of zeolites with BE A, MFI and FER structures with preparation of zeolitic products with the required concentration of aluminium atoms in Al pairs and concentrations of isolated Al atoms in the skeleton, where the total concentration of Al atoms in the skeleton is the sum of twice the concentration of Al pairs and the concentration of isolated Al atoms. The attained range of concentrations of aluminium atoms in Al pairs is from 5 to 85 % and the concentration of isolated Al atoms is in the range 15 to 95 % of the total concentration of aluminium atoms in the zeolite skeleton. Targeted selection of the initial sources of silicon and aluminium, their properties and process conditions of the synthesis yields zeolites with BEA, MFI and FER structures with aluminium atoms in the zeolite skeleton with predominance either in the form of Al pairs or in the form of isolated Al atoms. According to whether a zeolite with BEA, MFI or FER structure is required, the composition of the reaction gel and the synthesis conditions are simultaneously selected so that the zeolite with the corresponding structure is formed. Synthesis of zeolites with BEA, MFI and FER structure with controlled distribution of aluminium atoms in the skeleton according to the invention utilizes the different reactivities of sources of aluminium and silicon and different reactivities of silicate and alumino-silicate precursors, determined by the specific surface area and degree of cross-linking of the precursor. The distribution of the Al in the skeleton of zeolites with BEA, MFI and FER structure is controlled by the use of alkaline salts or alkaline silicates and the use of organic bases, seeding crystals and various ageing times.

The invention is related to the use of a suitable combination of various sources of aluminium, generally A1C1₃, A1(N0₃)3, NaOH and aluminium-tri-sec-butoxide, and sources of silicon, generally tetraethyl orthosilicate, Na-silicate, sol of silicic acid and amorphous nano-silicates, utilizing their different reactivities. An advantage lies in the use of silicate or alumino-silicate precursors with defined size of the amorphous particles and controlled reactivity, given by their specific surface area and degree of cross-linking, organic bases, inorganic cations and conditions for performance of the synthesis (use of seeding crystallites, time of ageing of the reaction mixture) for the required distribution of Al in the skeleton of the zeolitic products of the synthesis.

The precursor is a suspension of fine precipitated amorphous silicate or alumino-silicate with defined particle size from 3 to 10 nm with a specific surface area of 300 to 1000 m²/g and degree of cross-linking of 15 to 90 %, which has low viscosity and can be easily stirred even at high dry matter contents. Uniform distribution of the aluminium atoms in the precursor leads to regular arrangement of the aluminium atoms in the zeolite structure and reduces the formation of phase impurities.

The advantage of the use of silicate or alumino-silicate precursors of various reactivities lies in the possibility of controlled release of the skeletal components into the liquid phase. The reactivity of the silicate or alumino-silicate precursors depends on their specific surface. Its measurement is based on the principle of sorption of hydroxyl ions on the silicate or alumino- silicate interfaces by the titration method in aqueous suspensions. The reactivity of the silicate or alumino-silicate precursors also depends on their degree of cross-linking. Its characterization is based on the fact that the amount of Si0₂ released from the precursor into the liquid phase through the alkali treatment decreases with the degree of inter-connection of the silicon atoms into the branched structure. The rate of release of skeletal Si and Al components into the liquid phase, i.e. the reactivity of the precursor, must be controlled according to the values of the Si : Al molar ratio in the zeolitic product.

In products with resultant Si : Al ratio < 20 : 1, the formation of amorphous nanoparticles with the character of a zeolite structure is promoted by the use of a precursor with medium reactivity with a specific surface area of 600 to 800 m²/g and degree of cross-linking of Si0₂ of 70 to 90 %, i.e. with dense inter-connection of alumino-silicate chains into branched structures, where 70 to 90 % of the Si atoms are interconnected through oxygen atoms with more than two neighboring silicon atoms.

In products with resultant Si : Al ratio > 20 : 1, the formation of amorphous nanoparticles with the character of a zeolite structure is promoted by the use of a precursor with medium reactivity with a specific surface area of 700 to 1000 m²/g and degree of cross-linking of Si0₂ of 15 to 30 %, i.e. with low density of interconnection of alumino-silicate chains, where only 15 to 30 % of the Si atoms are inter-connected with more than two neighboring silicon atoms.

The concentration of Al pairs at the same concentration of aluminium atoms in the product increases with increasing concentration of nanoparticles (amorphous under X-ray) in the reaction mixture in the initial stage of the hydrothermal synthesis, which increases with longer times of ageing of the reaction mixture. An increase in the Si : Al molar ratio of the produced zeolite in the range 12 : 1 to 30 : 1 requires an increase in the concentration of oligomer, i.e. mono-penta-atomic Si0₂ (A1₂0₃) particles released from the source of skeletal components into the liquid phase of the reaction mixture.

A higher relative concentration of Al pairs in products with Si : Al > 20 : 1 is achieved by increasing the reactivity of sources of skeletal components, i.e. by suitable use of monomolecular tetraethyl orthosilicates in comparison with polymer amorphous nanosilica and Na-silicate and suitable use of A1C1₃ compared with A1(N0₃)3 and Al-tert-butoxide.

High relative concentrations of isolated Al atoms in the zeolite skeleton are achieved by suitable use of high concentrations of Na⁺ ions in the form of Na-salts or Na-silicates, a shorter period of ageing of the reaction mixture and the use of silicate and alumino-silicate precursors with the following parameters:

a) specific surface area 700 to 1 000 m²/g and degree of cross-linking of Si0₂ 15 to 30 % for zeolites with resultant Si : Al < 20 : 1 ; b) specific surface area 600 to 800 m²/g and degree of cross-linking of Si0₂ 70 to 90 % for zeolites with resultant Si : Al > 20 : 1.

A high relative concentration of Al pairs in the zeolite skeleton is achieved by using alumino- silicate precursors with the following parameters:

a) specific surface area 600 to 800 m²/g and degree of cross-linking of Si0₂ 70 to 90 % for zeolites with resultant Si : Al < 20 : 1 ;

b) specific surface area 700 to 1000 m²/g and degree of cross-linking of Si0₂ 15 to 30 % for zeolites with resultant Si : Al > 20 : 1.

Examples Example 1

A method of manufacture of zeolite with BEA structure with a molar ratio of Si : Al = 16.1 : 1 with high relative concentration of isolated Al atoms.

231 g of silicic acid sol containing 27.07 % wt. Si0₂ was mixed with 6.70 g of sodium aluminate and 3.98 g of sodium hydroxide in 43.5 g of water and with an aqueous solution containing 66 g of tetraethyl ammonium bromide dissolved in 124 g of 25 % solution of NH₄OH and 100 g of water and stirring for a period of 30 minutes. The resultant reaction mixture was intensely stirred for a period of 10 minutes.

Then 1.25 g of seeding crystals of zeolite with BEA structure were added to the reaction mixture and the mixture was left to age with continuous stirring for a period of 2 hours at laboratory temperature. The reaction mixture was placed in a mixing autoclave with a volume of 750 ml, where zeolite with BEA structure crystallized at a temperature of 140 °C for a period of 6 days. The product was the zeolite with BEA structure with molar ratios determined by X-ray spectral analysis, equal to Si : Al = 16.1 : 1 and Na : Al = 0.23 : 1. The Si : Al molar ratio in the skeleton of the product was determined from quantitative analysis of the ²⁹Si and ²⁷ Al MAS NMR spectra and corresponded to the value determined by X-ray spectral analysis. The concentration of Si(2Si2Al) atoms (Al-O-Si-O-Al sequence in the skeleton), determined from the Si MAS NMR spectra, was < 3% rel. of the Al content in the zeolite. The concentration of the Al-0-(Si-0)₂-Al sequence in the skeleton (Al pairs) was determined from the intensity of the d-d bands in the Vis spectra of the Co(II)-BEA zeolite with the maximum degree of exchange of Co(II) ions in the cationic positions, dehydrated at 450 °C for a period of 3 hours, and the corresponding absorption coefficients. The concentration of isolated Al atoms (Al-0-(Si-0)_n>2-Al) was calculated as the difference between the concentration of Al atoms in the skeleton and the concentration of Al atoms in Al pairs. The BEA zeolite exhibited 61 % Al in the form of isolated Al atoms.

Example 2

A method of manufacture of zeolite with BEA structure with a molar ratio of Si : Al = 13.5 : 1 with high relative concentration of aluminium in Al pairs.

The skeletal components were derived from an alumino-silicate precursor with medium activity, a specific surface area of 800 m²/g, degree of cross-linking of 85 % and molar ratio of Si : Al = 14 : 1, prepared by precipitating a solution of water glass containing 15 % wt. Si0₂ and 4.4 % wt. Na₂0 and a solution of aluminium sulphate and sulphuric acid containing 3.3 % wt. A1₂0₃ and 26.0 % wt. S0₄ ^2" at pH 7.5 to 8, filtered and freed of sodium sulphate by washing and ion exchanged with an ammonium nitrate solution. Then an aqueous solution of tetraethyl ammonium hydroxide was added so that the molar ratio in the reaction mixture was tetraethyl ammonium hydroxide : Si = 0.3 : 1. To accelerate the progress of the reaction, seeding crystals were added in an amount of 1 % wt. compared to the sum of the contents of Si0₂ and A1₂0₃ in the reaction mixture of the anticipated total weight of the product. The H₂0 : Si molar ratio was adjusted to a value of 12 : 1 by addition of water. Ageing of the reaction mixture for 10 minutes with continuous stirring was followed by hydrothermal synthesis in a stirred autoclave at a temperature of 135 °C for a period of 72 hours. The crystalline product was separated from the solution by filtration, washed with distilled water and dried in the air.

The product consisted in a zeolite with BEA structure and a molar ratio of Si : Al = 13.5 : 1, determined by X-ray spectral analysis. Using the method described in example 1, the BEA zeolite was found to contain 65 % of the Al atoms in the form of Al pairs.

Example 3

A method of manufacture of zeolite with MFI structure with a molar ratio of Si : Al = 28.6 : 1 with high relative concentration of isolated Al atoms. 0.74 g of aluminium-tri-sec-butoxide was dissolved in 10 ml of distilled water and then 22.6 g of tetraethyl orthosilicate and 5 ml of ethanol were added at laboratory temperature with continuous stirring. The resultant reaction mixture was stirred for a period of 90 minutes at laboratory temperature. Then 40.75 ml of tetrapropyl ammonium hydroxide were dissolved in 40 ml of distilled water and stirred for a period of 90 minutes. Then the two reaction components were mixed together and the mixture was left to age with continuous stirring for a period of 90 minutes. The zeolite was left to crystallize for a period of 5 to 7 days at a temperature of 150 to 170 °C.

The product consisted in a zeolite with MFI structure and a molar ratio of Si : Al = 28.6 : 1, determined by X-ray spectral analysis. Using the method described in example 1, the MFI zeolite was found to contain 94 % of the Al atoms in the form of isolated Al atoms.

Example 4

A method of manufacture of zeolite with MFI structure with a molar ratio of Si : Al = 14.6 : 1 with high relative concentration of isolated Al atoms.

1.4 g of A1(N0₃)₃.9H₂0 were dissolved in 10 ml of distilled water and then 24.5 g of sodium silicate were added (27 % wt. Si0₂, 10 % wt. NaOH). The resultant reaction mixture was stirred for a period of 90 minutes at laboratory temperature. Then 40.75 ml of tetrapropyl ammonium hydroxide were dissolved in 40 ml of distilled water and stirred for a period of 90 minutes. Then the two components were mixed together and the mixture was left to age with continuous stirring for a period of 90 minutes. The zeolite was left to crystallize for a period of 5 to 7 days at a temperature of 150 to 170 °C.

The product consisted in a zeolite with MFI structure and a molar ratio of Si : Al = 14.6 : 1, determined by X-ray spectral analysis. Using the method described in example 1, the MFI zeolite was found to contain 92 % of the Al atoms in the form of isolated Al atoms.

Example 5

A method of manufacture of zeolite with MFI structure with a molar ratio of Si : Al = 20.9 : 1 with high relative concentration of Al in Al pairs.

0.87 g of A1C1₃.6H₂0 was dissolved in 10 ml of distilled water and then 22.6 g of tetraethyl orthosilicate and 5 ml of ethanol were added at laboratory temperature with continuous stirring. Then 15 ml of NaOH solution containing 36 mmol of NaOH were added with continuous stirring. The mixture was stored for 90 minutes at laboratory temperature. Then 40.75 ml of tetrapropyl ammonium hydroxide, prior dissolved in 40 ml of distilled water, were added and the mixture was stirred for a period of 90 minutes. The reaction mixture was left to age with continuous stirring for a period of 90 minutes. The zeolite was left to crystallize for a period of 5 to 7 days at a temperature of 150 to 170 °C.

The product consisted in a zeolite with MFI structure and with a molar ratio of Si : Al = 20.9 : 1, determined by X-ray spectral analysis. Using the method described in example 1, the MFI zeolite was found to contain 58 % of the Al atoms in the form of Al pairs.

Example 6

A method of manufacture of zeolite with MFI structure with a molar ratio of Si : Al = 12.1 : 1 with high relative concentration of isolated Al atoms.

The skeletal components were derived from an alumino-silicate precursor with high reactivity with a specific surface area of 950 m²/g, degree of cross-linking of 20 % and molar ratio of Si : Al - 13 : 1, prepared by precipitating a silicic acid sol containing 30 % wt. Si0₂ with an aqueous solution of aluminium hydroxy chloride containing 15 % wt. A1₂0₃. Then ethanol and an aqueous solution of NaOH were added. The molar ratio of the reaction mixture corresponded to ethanol : Si = 0.5 : 1, ammonia : Si = 0.25 : 1, OH : Si = 0.13 : 1 and H₂0 : Si = 18 : 1. Ageing of the reaction mixture for ten minutes with continuous stirring was followed by hydrothermal synthesis in a stirred autoclave at a temperature of 160 °C for a period of 20 hours. The crystalline product was separated from the solution by filtration, washed with distilled water and dried in the air.

The product consisted in a zeolite with MFI structure and a molar ratio of Si : Al = 12.1 : 1, determined by X-ray spectral analysis. Using the method described in example 1, the MFI zeolite was found to contain 90 % of the Al atoms in the form of isolated Al atoms.

Example 7

A method of manufacture of zeolite with MFI structure with a molar ratio of Si : Al = 13.0 : 1 with high relative concentration of Al pairs.

2.51 g of A1C1₃.6H₂0 were dissolved in 30 ml of distilled water and then 25 g of silica sol (30 % wt.) were added. Then 0.7 g of NaOH were dissolved in 29 g of distilled water and mixed with 20.8 g of 25 % wt. ammonium hydroxide and 8 g ethanol. The two reaction mixtures were then mixed together with continuous stirring. The reaction mixture exhibited the following ratios Si : Al = 12 : 1, H₂0 : Si = 41 : 1, OH^" : Si = 0.14 : 1, ethanol : Si = 1.4 : 1 and NH4OH : Si = 1.19 : 1. The mixture was left to age with stirring for a period of 10 minutes. The reaction mixture was left to crystallize in a stirred autoclave for a period of 50 hours at a temperature of 167 °C.

The product consisted in a zeolite with MFI structure and a molar ratio of Si : Al = 13.0 : 1, determined by X-ray spectral analysis. Using the method described in example 1, the MFI zeolite was found to contain 84 % of the Al atoms in the form of Al pairs.

Example 8

A method of manufacture of zeolite with MFI structure with a molar ratio of Si : Al = 12.4 : 1 with high relative concentration of Al pairs.

The skeletal components were derived from a silicate precursor with medium activity, a specific surface area of 700 m²/g, degree of cross-linking of 80 %, prepared by precipitating a solution of water glass containing 15 % wt. S1O2 and 4.4 % wt. Na₂0 and a solution of sulphuric acid containing 23.0 % wt. S0₄ ^2" at pH 7.5 to 8.0, filtered and freed of sodium sulphate by washing. Then ethanol, ammonia, aqueous solution of NaOH and sodium aluminate were added. The molar ratio of the reaction mixture corresponded to ethanol : Si = 0.5 : 1, ammonia : Si = 0,25 : 1, OH : Si - 0.18 : 1 and Si : Al = 14 : 1. To accelerate the progress of the reaction, seed crystals of zeolite with MFI structure were added in an amount of 1 % wt. compared to the sum of the contents of Si0₂ and A1₂0₃ in the reaction mixture. The H₂0 : Si molar ratio in the reaction mixture was 5 : 1. Ageing of the reaction mixture for ten minutes with continuous stirring was followed by hydrothermal synthesis in a stirred autoclave at a temperature of 160 °C for a period of 20 hours. The crystalline product was then separated from the solution by filtration, washed with distilled water and dried in the air.

The product consisted in a zeolite with MFI structure and a molar ratio of Si : Al = 12.4 : 1, determined by X-ray spectral analysis. Using the method described in example 1, the MFI zeolite was found to contain 50 % of the Al atoms in the form of Al pairs. Example 9

A method of manufacture of zeolite with MFI structure with a molar ratio of Si : Al = 35.0 : 1 with high relative concentration of isolated Al atoms.

The skeletal components were derived from an alumino-silicate precursor with medium activity, a specific surface area of 800 m²/g, degree of cross-linking of 85 % and molar ratio of Si : Al - 40 : 1, prepared by precipitating a solution of water glass containing 15 % wt. SiC*2 and 4.4 % wt. Na₂0 and a solution of aluminium sulphate and sulphuric acid containing 1.2 % wt. A1₂0₃ and 25 % wt. S0₄ ^2" at pH 7.5 to 8.0, followed by filtration and freed from sodium sulphate by washing. Then tetrapropyl ammonium bromide and an aqueous solution of NaOH were added. The molar ratio of the reaction mixture corresponded to tetrapropyl ammonium bromide : Si = 0.006 : 1, OH : Si = 0.13 : 1 and H₂0 : Si = 8 : 1. To accelerate the progress of the reaction, seeding crystals were added in an amount of 1 % wt. compared to the sum of the contents of Si0₂ and A1₂0₃ in the reaction mixture. The reaction mixture was left to age with continuous stirring for a period of 12 hours at laboratory temperature. Then water was added to a molar ratio of H₂0: Si = 21 : 1. This was followed by hydrothermal synthesis in a stirred autoclave at a temperature of 160 °C for a period of 20 hours. The crystalline product was then separated from the solution by filtration, washed with distilled water and dried in the air.

The product consisted in a zeolite with MFI structure and a molar ratio of Si : Al = 35.0 : 1, determined by X-ray spectral analysis. Using the method described in example 1, the MFI zeolite was found to contain 90 % of the Al atoms in the form of isolated Al atoms.

Example 10

A method of manufacture of zeolite with MFI structure with a molar ratio of Si : Al = 34.2 : 1 with high relative concentration of Al pairs.

The skeletal components were derived from an alumino-silicate precursor with high reactivity with a specific surface area of 800 m²/g, degree of cross-linking of 20 % and molar ratio of Si : Al = 40 : 1, prepared by precipitating a silicic acid sol containing 40 % wt. Si0₂ with an aqueous solution of polyaluminium chloride containing 15 % wt. A1₂0₃. Then tetrapropyl ammonium bromide and an aqueous solution of NaOH were added to the source of skeletal components. The molar ratio of the reaction mixture corresponded to tetrapropyl ammonium bromide : Si = 0.006 : 1, OH : Si = 0.13 : 1 and H₂0 : Si = 8 : 1. To accelerate the progress of the reaction, seeding crystals were added in an amount of 1 % wt. compared to the sum of the contents of Si0₂ and A1₂C«3 in the reaction mixture. The reaction mixture was left to age at continuous stirring for a period of 12 hours at laboratory temperature. Then water was added to a molar ratio of H₂0: Si = 21 : 1. This was followed by hydrothermal synthesis in a stirred autoclave at a temperature of 160 °C for a period of 20 hours. The crystalline product was separated from the solution by filtration, washed with distilled water and dried in the air.

The product consisted in a zeolite with MFI structure and a molar ratio of Si : Al = 34.2 : 1, determined by X-ray spectral analysis. Using the method described in example 1, the MFI zeolite was found to contain 51 % of the Al atoms in the form of Al pairs.

Example 11

A method of manufacture of zeolite with MFI structure with a molar ratio of Si : Al = 30.1 : 1 with high relative concentration of Al pairs.

The skeletal components were derived from a silicate precursor with high reactivity with a specific surface area of 800 m /g and degree of cross-linking of 20 %, prepared by precipitating a silicic acid sol containing 40 % wt. Si0₂ with an aqueous solution of nitric acid containing 5 % wt. HN0₃. Then tetrapropyl ammoniun bromide, aqueous solution of NaOH and sodium aluminate were added to the precursor. The molar ratio of the reaction mixture corresponded to tetrapropyl ammonium bromide : Si = 0.006 : 1, OH : Si = 0.13 : 1, Si : Al = 40 : 1 and H₂0 : Si = 8 : 1. To accelerate the progress of the reaction, seed crystals were added in an amount of 1 % wt. compared to the sum of the contents of Si0₂ and A1₂0₃ in the reaction mixture. The reaction mixture was left to age with continuous stirring for a period of 12 hours at laboratory temperature. Then water was added to a molar ratio of H₂0: Si = 21 : 1. This was followed by hydrothermal synthesis in a stirred autoclave at a temperature of 160 °C for a period of 20 hours. The crystalline product was separated from the solution by filtration, washed with distilled water and dried in the air.

The product consisted in a zeolite with MFI structure and a molar ratio of Si : Al = 30.1 : 1, determined by X-ray spectral analysis. Using the method described in example 1, the MFI zeolite was found to contain 60 % of the Al atoms in the form of Al pairs. Example 12

A method of manufacture of zeolite with FER structure with a molar ratio of Si : Al = 9.8 : 1 with high relative concentration of Al pairs.

The skeletal components were derived from an alumino-silicate precursor with medium reactivity, a specific surface area of 650 m /g, degree of cross-linking of 80 % and molar ratio of Si : Al - 14 : 1, prepared by precipitating a solution of water glass containing 20 % wt. Si0₂ and 5.9 % wt. Na₂0 and a solution of aluminium sulphate and sulphuric acid containing 3.3 % wt. A1₂0₃ and 26.0 % wt. S0₄ ^2" at pH 7.5 to 8.0, followed by filtration and freed from sulphates by washing. KOH and NaOH were added to the precursor. The molar ratio was KOH : Si = 0.1 : 1 and NaOH : Si = 0.075 : 1. Then water was added to the reaction mixture to a molar ratio of H₂0: Si = 20 : 1. To accelerate the progress of the reaction, the mixture was seeded with 3 % wt. of ferrierite crystals compared to the sum of the contents of Si0₂ and A1₂0₃ in the reaction mixture. Ageing of the reaction mixture for ten minutes with continuous stirring was followed by hydrothermal synthesis in a stirred autoclave for a period of 72 hours at a temperature of 160 °C.

The product consisted in a zeolite with FER structure and a molar ratio of Si : Al = 9.8 : 1, determined by X-ray spectral analysis. Using the method described in example 1, the FER zeolite was found to contain 65 % of the Al atoms in the form of Al pairs.

Example 13

A method of manufacture of zeolite with FER structure with a molar ratio of Si : Al = 10.2 : 1 with high relative concentration of isolated Al atoms.

The skeletal components were derived from an alumino-silicate precursor with high reactivity with a specific surface area of 850 m²/g, degree of cross-linking of 15 % and molar ratio of Si : Al = 14 : 1, prepared by precipitating a silicic acid sol containing 30 % wt. Si0₂ with an solution of aluminium nitrate containing 1.0 % wt. A1₂0₃ and 3.7 % wt. NO3^'. KOH and NaOH were added to the precursor. The molar ratio was KOH : Si = 0.1 : 1 and NaOH : Si = 0.075 : 1. Then water was added to the reaction mixture to a molar ratio of H₂0: Si = 20 : 1. To accelerate the progress of the reaction, the mixture was seeded with 3 % wt. ferrierite crystals compared to the sum of the contents of Si0₂ and A1₂0₃ in the reaction mixture. Ageing of the reaction mixture for ten minutes with continuous stirring was followed by the hydrothermal part of the synthesis in a stirred autoclave for a period of 72 hours at a temperature of 160 °C.

The product consisted in a zeolite with FER structure and a molar ratio of Si : Al = 10.2 : 1, determined by X-ray spectral analysis. Using the method described in example 1, the FER zeolite was found to contain 80 % of the Al atoms in the form of isolated Al atoms.

Industrial Applicability

The method of manufacture of zeolites with pentasil structure with controlled distribution of aluminium atoms in the skeleton can be used industrially for the manufacture of zeolites and catalysts derived from them, containing the cations of transition metals for redox reactions, selective reduction of NO_x by ammonia and hydrocarbons, decomposition of dinitrous oxide and selective oxidation of hydrocarbons, and catalysts containing protons for acid-catalyzed transformation of olefins, transformation of methanol to olefins or aromates and cracking and isomerisation of paraffins.

Claims

C L A I M S

1. A method of manufacture of zeolites with pentasil structure with controlled distribution of aluminium atoms in the skeleton consisting in that the source of at least one substance selected from the group including aluminium and silicon is mixed at least with an aqueous solution of at least one substance taken from the group including sodium hydroxide, potassium hydroxide, sodium aluminate, ethanol, ammonia, a quaternary ammonium organic template, which is at least one of the substances selected from the group including tetraethyl ammonium bromide, tetrapropyl ammonium bromide, tetraethyl ammonium hydroxide and tetrapropyl ammonium hydroxide, where the molecular ratios in the reaction mixture are Si : Al = 7.5 : 1 to 90 : 1 and H₂0 : Si0₂ = 5 : 1 to 50 : 1, the reaction mixture is left to age at laboratory temperature with mixing for a period of at least 10 minutes and is then left to crystallize under hydrothermal conditions at a temperature of 130 to 170 °C for a period of at least 15 hours, where the skeleton of the zeolite formed contains Si and Al in a molar ratio of Si : Al = 8 : 1 to 40 : 1, wherein the kinetics of synthesis of the zeolite is controlled by the selection of the source of at least one of the substances selected from the group including aluminium and silicon, where this source is selected particularly from the group including sources with a specific surface area of 600 to 1000 m /g and degree of cross-linking of 15 to 90 %, where the skeleton of the zeolite formed contains 5 to 85 % aluminium atoms in the form of Al pairs and 15 to 95 % of the aluminium atoms in the form of isolated Al atoms.

2. The method of manufacture according to claim 1, wherein at first an amorphous precursor is advantageously prepared with a specific surface area of 600 to 800 m7g and degree of cross-linking of 70 to 90 % in that, at pH 7.5 to 8, an aqueous solution of sodium silicate containing 10 to 20 % wt. Si0₂ and 2.9 to 5.9 % wt. Na₂0 is precipitated with an aqueous solution containing at least one substance selected from the group including aluminium sulphate, aluminium nitrate with a total content of 1 to 5 % wt. A1₂0₃, 10 to 40 % wt. H₂S0₄ and 10 to 40 % wt. HN0₃, and then the liquid phase is separated from the precipitated precursor.

3. The method of manufacture according to claim 1, wherein at first an amorphous precursor is advantageously prepared with a specific surface area of 700 to 1000 m7g and degree of cross-linking of 15 to 30 % in that an aqueous solution of a salt of silicic acid containing 10 to 40 % wt. Si0₂ is precipitated by an aqueous solution containing at least one substance selected from the group including aluminium nitrate with a content of 0.5 to 2 % wt. A1₂0₃, polyaluminium chloride containing up to 20 % wt. A1₂0₃ and 2.5 to 5 % wt. HN0₃, and then the liquid phase is separated from the precipitated precursor.

4. The method of manufacture according to claim 1, wherein the source of the silicon, which is a sol of silicic acid, is mixed with an aqueous solution containing sodium aluminate, sodium hydroxide and a mixture of template, containing an aqueous solution of ammonium hydroxide and tetramethyl ammonium bromide, and with seeding crystals of zeolite with structure BEA in an amount of up to 10 % wt. in relation to the sum of the contents of Si0₂ and A1₂0₃ in the reaction mixture, where the molar ratios in the reaction mixture are Si : Al = 12 : 1 to 25 : 1, tetraethyl ammonium bromide : Si = 0.2 : 1 to 0.5 : 1, Na : Si = 0.05 : 1 to 0.3 : 1 and NFLjOH : Si = 0.5 : 1 to 2 : 1, the reaction mixture is left to age and is then crystallized at a temperature of 130 to 150 °C for a period of at least 5 days, where the skeleton of the formed zeolite with BEA structure with molecular ratio Si : Al = 12 : 1 to 25 : 1 contains 40 to 95 % of the aluminium atoms in the form of isolated Al atoms.

5. The method of manufacture according to claim 2, wherein the source of silicon and aluminium, preferably consisting in the amorphous precursor with a molar ratio of Si : Al = 12 : 1 to 20 : 1 washed with an ammonium nitrate solution with a concentration of 0.5 mol/1 is mixed with an aqueous solution containing tetraethyl ammonium hydroxide and with seeding crystals of zeolite with BEA structure in an amount of up to 10 % wt. in relation to the sum of the contents of Si0₂ and A1₂0₃ in the reaction mixture, where the molar ratios in the reaction mixture are tetraethyl ammonium bromide : Si0₂ = 0.1 : 1 to 1 : 1 and H₂0 : Si0₂ = 5 : 1 to 20 : 1, the reaction mixture is left to age and then to crystallize at a temperature of 130 to 150 °C for a period of 2 to 5 days, where the skeleton of the formed zeolite with BEA structure with molar ratio Si : Al = 12 : 1 to 20 : 1 contains 30 to 65 % aluminium atoms in the form of Al pairs.

6. The method of manufacture according to claim 1, wherein the source of silicon and aluminium is a substance prepared by the reaction of sodium sulphate, stirring for a period of at least 60 minutes at laboratory temperature, with a solution of at least one substance selected from the group including aluminium nitrate and aluminium chloride, and with an aqueous solution containing tetrapropyl ammonium hydroxide, where the molar ratios in the reaction mixture are Si : Al = 20 : 1 to 90 : 1 , tetrapropyl ammonium hydroxide : Si0₂ = 0.3 : 1 to 0.6 : 1, OH : Si = 0.3 : 1 to 0.6 : 1 and H₂0 : Si0₂ = 20 : 1 to 30 : 1, the reaction mixture is left to age with stirring for a period of at least 60 minutes and then to crystallize at a temperature of 150 to 170 °C for a period of at least 3 days, where the skeleton of the formed zeolite with MFI structure with a molar ratio of Si : Al = 12 : 1 to 40 : 1 contains 80 to 95 % aluminium atoms in the form of isolated Al atoms.

7. The method of manufacture according to claim 1 , wherein the source of silicon and aluminium is advantageously a substance prepared by the reaction of tetraethyl orthosilicate dissolved in ethanol with stirring for a period of at least 60 minutes at laboratory temperature with at least one substance selected from the group including aluminium-tri-sec-butoxide and aluminium nitrate, and with the aqueous solution containing tetrapropyl ammonium hydroxide, where the molar ratios in the reaction mixture are Si : Al = 20 : 1 to 90 : 1, tetrapropyl ammonium hydroxide : Si0₂ = 0.3 : 1 to 0.6 : 1, , Na₂0 : Si0₂ = 0 : 1 to 0.2 : 1, OH : Si = 0.3 : 1 to 0.4 : 1, ethanol : Si0₂ = 1 : 1 to 1.8 :1 and H₂0 : Si0₂ = 20 : 1 to 45 : 1 , the reaction mixture is left to age with stirring for a period of at least 60 minutes and then to crystallize at a temperature of 150 to 170 °C for a period of at least 3 days, where the skeleton of the formed zeolite with MFI structure with a molar ratio of Si : Al = 12 : 1 to 40 : 1 contains 80 to 95 % aluminium atoms in the form of isolated Al atoms.

8. The method of manufacture according to claim 1, wherein the source of silicon and aluminium is preferably a substance prepared by the reaction of tetraethyl orthosilicate dissolved in ethanol with stirring for a period of at least 60 minutes at laboratory temperature with at least one substance selected from the group including aluminium chloride and aluminium hydroxide, dissolved in water with the addition of sodium cations in the form of at least one substance selected from the group including NaOH and Na₃P0₄, in an amount of up to 56 mmol Na⁺ ions per 100 ml of reaction mixture, and an aqueous solution containing tetrapropyl ammonium hydroxide, where the molar ratios in the reaction mixture are Si : Al = 7.5 : 1 to 45 : 1, tetraethyl ammonium hydroxide : Si0₂ = 0.3 : 1 to 0.6 : 1, Na₂0 : Si0₂ = 0 : 1 to 0.2 : 1, OH : Si = 0.3 : 1 to 0.4 : 1, ethanol : SiQ₂ = 1 : 1 to 1.8 :1 and H₂0 : Si0₂ = 20 : 1 to 30 : 1, the reaction mixture is left to age with stirring for a period of at least 60 minutes and then to crystallize at a temperature of 140 to 160 °C for a period of at least 3 days, where the skeleton of the formed zeolite with MFI structure with a molar ratio of Si : Al = 15 : 1 to 40 : 1 contains 26 to 58 % aluminium atoms in the form of Al pairs.

9. The method of manufacture according to claim 3, wherein the amorphous precursor is mixed with an aqueous solution containing at least one substance selected from a group including ethanol, ammonia, sodium hydroxide and sodium aluminate, and with seeding crystals with MFI structure in an amount of 0.2 to 2 % wt. compared to the sum of the contents of Si0₂ and AI2O3 in the reaction mixture, where the molar ratios of the reaction mixture are Si : Al = 12 : 1 to 20 : 1, Na₂0 : Si0₂ - 0.02 : 1 to 0.15 : 1 and NH₄OH : Si0₂ = 0.2 : 1 to 1 : 1, ethanol : Si0₂ = 0.3 : 1 to 0.8 : 1, OH : Si0₂ = 0.1 : 1 to 0.3 : 1 and H₂0 : Si0₂ = 10 : 1 to 20 : 1, the reaction mixture is left to age for a period of at least 10 minutes and then to crystallize at a temperature of 150 to 170 °C for a period of 15 to 48 hours, where the skeleton of the formed zeolite with MFI structure with a molar ratio of Si : Al = 12 : 1 to 20 : 1 contains 60 to 95 % aluminium atoms in the form of isolated Al atoms.

10. The method of manufacture according to claim 2, wherein the amorphous precursor is mixed with an aqueous solution containing at least one substance selected from a group including ethanol, ammonia, sodium hydroxide and sodium aluminate, and with seeding crystals with MFI structure in an amount of 0.2 to 2 % wt. compared to the sum of the contents of Si0₂ and A1₂0₃ in the reaction mixture, where the molar ratios in the reaction mixture are Si : Al = 12 : 1 to 20 : 1, Na₂0 : Si0₂ = 0.02 : 1 to 0.15 : 1 and NH₄OH : Si0₂ = 0.2 : 1 to 1 : 1, ethanol : Si0₂ = 0.3 : 1 to 0.8 : 1, OH : Si0₂ = 0.1 : 1 to 0.3 : 1 and H₂0 : Si0₂ = 4 : 1 to 8 : 1, the reaction mixture is left to age with stirring for a period of at least 10 minutes and is then left to crystallize at a temperature of 150 to 170 °C for a period of 15 to 48 hours, where the skeleton of the formed zeolite with MFI structure with a molar ratio of Si : Al = 12 : 1 to 20 : 1 contains 30 to 60 % aluminium atoms in the form of Al pairs.

11. The method of manufacture according to claim 2, wherein the amorphous precursor is preferably mixed with an aqueous solution containing at least one substance selected from a group including sodium hydroxide, sodium aluminate and tetrapropyl ammonium bromide, and with seeding crystals with MFI structure in an amount of 0.2 to 2 % wt. compared to the sum of the contents of Si0₂ and AI2O3 in the mixture, where the molar ratios in the reaction mixture are Si : Al at least 20 : 1, Na₂0 : Si0₂ =

0.02 : 1 to 0.15 : 0.01 and tetrapropyl ammonium bromide : Si0₂ = 0.002 : 1 to 0.01 :

1, OH : Si0₂ = 0,1 : 1 to 0.3 : 1 and H₂0 : Si0₂ = 4 : 1 to 8 : 1, the reaction mixture is left to age with stirring for a period of at least 12 hours and then water is added to the reaction mixture, where the molar ratio H₂0 : Si0₂ = 20 : 1 to 30 : 1, and then the reaction mixture is left to crystallize at a temperature of 150 to 170 °C for a period of 15 to 48 hours, where the skeleton of the formed zeolite with MFI structure with a molar ratio of Si : Al = 20 : 1 to 40 : 1 contains 60 to 95 % aluminium atoms in the form of isolated Al atoms.

12. The method of manufacture according to claim 3, wherein the amorphous precursor is mixed with an aqueous solution containing at least one substance selected from a group including sodium hydroxide, sodium aluminate and tetrapropyl ammonium bromide, and with seeding crystals of the zeolite with MFI structure in an amount of 0.2 to 2 % wt. compared to the sum of the contents of Si0₂ and A1₂0₃ in the mixture, where the molar ratios in the reaction mixture are Si : Al at least 20 : 1, Na₂0 : Si0₂ = 0.02 : 1 to 0.15 : 0.01, tetrapropyl ammonium bromide : Si0₂ = 0.002 : 1 to 0.01 : 1, OH : Si0₂ = 0.1 : 1 to 0.3 : 1 and H₂0 : Si0₂ = 6 : 1 to 10 : 1, the reaction mixture is left to age with stirring of a period of at least 12 hours and then water is added to the reaction mixture, where the molar ratio H₂0 : Si0₂ = 15 : 1 to 30 : 1, and then the reaction mixture is left to crystallize at a temperature of 150 to 170 °C for a period of 15 to 48 hours, where the skeleton of the formed zeolite with MFI structure with a molar ratio of Si : Al = 20 : 1 to 40 : 1 contains 30 to 50 % aluminium atoms in the form of Al pairs.

13. The method of manufacture according to claim 2, wherein the amorphous precursor is mixed with an aqueous solution containing at least one substance selected from a group including sodium hydroxide and potassium hydroxide, and with seeding crystals with FER structure in an amount of 2 to 4 % wt. compared to the sum of the contents of Si0₂ and A1₂0₃ in the mixture, where the molar ratios in the reaction mixture are Si : Al = 8 : 1, Na : Si = 0.05 : 1 to 0.3 : 1, K : Si = 0.075 : 1 to 0.15 : 1 and H₂0 : Si = 15 : 1 to 25 : 1, the reaction mixture is left to age for a period of at least 10 minutes and then to crystallize at a temperature of 150 to 170 °C for a period of at least 2 days, where the skeleton of the formed zeolite with FER structure with a molar ratio of Si : Al = 8 : 1 to 20 : 1 contains 30 to 60 % aluminium atoms in the form of Al pairs.

14. The method of manufacture according to claim 3, wherein the amorphous precursor is advantageously mixed with an aqueous solution containing at least one substance selected from a group including sodium hydroxide and potassium hydroxide, and with seeding crystals with FER structure in an amount of 2 to 4 % wt. compared to the sum of the contents of Si0₂ and A1₂0₃ in the mixture, where the molar ratios in the reaction mixture are Si : Al = 8 : 1 to 20 : 1, Na : Si = 0.05 : 1 to 0.3 : 1, K : Si = 0.075 : 1 to 0.15 : 1 and H₂0 : Si = 15 : 1 to 25 : 1, the reaction mixture is left to age for a period of at least 10 minutes and then to crystallize at a temperature of 150 to 170 °C for a period of at least 2 days, where the skeleton of the formed zeolite with FER structure with a molar ratio of Si : Al = 8 : 1 to 20 : 1 contains 40 to 80 % aluminium atoms in the form of isolated Al atoms.