RU2420455C1 - Method of producing mesoporous amorphous composite elementosilicates - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: invention relates to synthesis of mesoporous materials and specifically to a method of producing mesoporous amorphous composite elementosilicates. The method of producing mesoporous amorphous composite elementosilicates is realised by treating a mixture of salt solutions of one or more metals and ethylsilicate -40 with aqueous ammonium solution, followed by drying the formed paste in air at atmospheric pressure at 100-150C for 4-6 hours. The obtained xerogel is then heated at a rate of 2-5C per minute to 500-650C, annealed at that temperature for 4-6 hours and then crushed. ^ EFFECT: invention speeds up the process of formation of mesoporous amorphous composite elementosilicates; lowers production cost compared to existing methods; enables to obtain active silicate catalysts with one or more metals from a wide range of elements which are uniformly distributed in a silicate matrix. ^ 5 cl, 2 dwg, 2 tbl, 9 ex

Description

The invention relates to the field of synthesis of mesoporous materials, and in particular to a method for producing mesoporous amorphous mixed elementosilicates.

Elementosilicates, in particular titanosilicates, are known as active catalysts for a large number of reactions: alkylation of benzene with ethylene, hydrocracking, isomerization of paraffins and naphthenes, polymerization of olefins, oxidation of hydrocarbons (eg, benzene and phenol), etc. [Pat. RF 2076775, 1997; Pat. USA 5935895, 1999].

Accelerated development of studies on the synthesis and use of catalytically active elemental silicates occurred after the implementation in 1986 by Enichem in Italy of an industrial process for the oxidation of phenol with hydrogen peroxide in the presence of the TS-1 microporous titanosilicate catalyst [Pat. US 4410501, C01B 33/20, 1983; RU 2076775].

According to the patent, a catalyst of the composition xTi · (1-x) SiO ₂ , where x = 0.0005-0.04, is obtained by hydrothermal autoclaving of a mixture containing a source of silicon oxide, titanium oxides, nitrided organic base and water, separating crystals from stock solution, washing, drying and calcining them.

As a template, R ₄ NOH (nitrated organic base) with a ratio of R ₄ N ⁺ / SiO ₂ 0.1: 2.0, tetraethylammonium hydroxide is usually used. Tetraethylorthosilicate is used as a source of silicon oxide, and tetraethylorthotitanate, Ti (OC ₂ H ₅ ) ₄ is used as a source of titanium oxide. According to the patent, hydrothermal treatment is carried out at 130-200 ° C in an autoclave under pressure for 6-30 days, and calcining for 1-72 hours at 550 ° C.

Despite the consumption of expensive reagents, especially the template, and the need for a multi-day hydrothermal charge treatment in an autoclave, the TS-1 catalyst remains the best catalyst for the oxidation of organic compounds with hydrogen peroxide.

The main disadvantage of microporous catalysts of the TS-1 type is the small pore size, which makes them impossible to use in reactions involving the conversion of large molecules.

In the last decade, the number of works on the synthesis, research, and application of new materials — mesoporous silicates containing ions of various transition metals — has grown rapidly.

There are two fundamentally different types of mesoporous metallosilicate materials: ordered and disordered. The first type includes various mesostructured materials (MMM, MSM-41, MSM-48, etc.), which are often called mesoporous molecular sieves, and the second type includes amorphous mixed oxides.

The latter are structurally long chains consisting of primary particles (globules) of silica, which have a small number of points of contact. Mixed oxides are obtained by the sol-gel method, which includes five main steps:

1) acid or alkaline hydrolysis of silicon alkoxides and a transition metal;

2) polycondensation of alkoxides and the growth of sol particles;

3) aggregation of sols into the alcohol net;

4) aging of the gel;

5) drying and calcination.

According to this technology, the synthesis of mixed silicon-titan-catalysts effective in olefin epoxidation processes described in patent US 5935895. The hydrolysis of silicon alkoxide and titanalkoksihelatnogo complex, dispersed in an alcohol ROH (wherein R = C ₁ -C _4), is carried out in an acidic medium. The sol obtained after the polycondensation of hydroxides is stirred in an atmosphere of dry inert gas. The gel is dried under supercritical conditions in liquid CO ₂ . Depending on the drying conditions, amorphous mixed oxides are obtained as aerogels (average pore size greater than 100 Å, specific surface area> 1000 m ² / g) or as xerogels (average pore size 5-20 Å, specific surface area 300-700 m ² / d). Aerogels are formed during the drying of alcohol under conditions of a constant increase in the temperature and pressure of the solvent (alcohol or carbon dioxide) to supercritical values. Xerogels are obtained by conventional thermal drying.

An improvement of the method for producing mixed titanosilicate oxides is given in RF patent No. 2196764 (2003).

The catalyst is prepared as follows. The acid hydrolysis of tetraethoxyorthosilicate (TEOS) is carried out for 3 hours at 50 ° C. Then, titanium is added to the hydrolyzed TEOS solution in the form of an alkoxide chelate complex dissolved in ethanol, which is formed from titanium alkoxide of the general formula Ti (OR) ₄ , where R = C ₁ -C ₄ alkyl, and acetylacetone, and heated for 2 hours at 50 ° FROM. Then a solution of ethyl silicate-40 in ethanol is added and the products obtained are condensed - silicon, titanium and low molecular weight polysilicate hydroxides under neutral or alkaline conditions in the presence of a basic catalyst (ammonium hydroxide or tetramethylammonium hydroxide). After gelation, the alcohol is left in a closed glass, where the aging process takes 7 days at room temperature. The gel is dried either in a stream of supercritical CO ₂ at a temperature of 50-70 ° C and a pressure of 120-180 bar to form a titanosilicate airgel, or in air at a temperature of 30 to 85 ° C and pressure from atmospheric to 0.05 bar with the formation of mesoporous titanosilicate xerogel. Before use, the catalyst is calcined at a temperature of from 100 to 600 ° C.

The disadvantages of these methods of preparation of amorphous mixed oxide elementosilicates is the complexity of the technology, the use of expensive reagents and equipment, the ability to use only alkoxides of a limited range of metals.

The objectives of the present invention are: 1) to develop a method for producing mesoporous amorphous mixed elementosilicates with the possibility of involving in the composition of almost any metal of the Periodic system of elements or simultaneously several metals; 2) a significant simplification of the method and lower costs for the preparation of catalysts.

The solution of these problems is achieved by the fact that the method of producing mesoporous amorphous mixed elementosilicates is carried out by processing a mixture of solutions of salts of one or more metals and ethyl silicate-40 with an aqueous solution of ammonia, followed by drying the resulting paste in air at atmospheric pressure at 100-150 ° C for 4- 6 o'clock. The resulting xerogel is then heated at a speed of 2-5 ° C per minute to 500-650 ° C, calcined at this temperature for 4-6 hours and ground.

Chlorides, nitrates, acetates Al, Ti, Fe, Zr, Sn, Ca, Cu, Mn, Cr and other metals soluble in ethanol or other organic solvents are used as salts.

The atomic ratio of silicon: metal in the initial mixture was changed from 100: 1 to 2: 1.

The ammonia consumption for producing xerogel was 1.0 ± 0.1 equivalent per salt equivalent +30 mmol per 100 g of ethyl silicate-40.

Using the proposed method allows you to:

1) significantly accelerate the production of mesoporous amorphous mixed elementosilicates due to faster hydrolysis, polycondensation, sol - and gel formation during the processing of the initial mixture with ammonia water;

2) reduce the cost of preparing catalysts through the use of cheaper than tetraethylorthosilicate, ethyl silicate-40 and due to the rejection of the use of expensive templates and their disposal;

3) use the relatively cheap salts of most metals of the Periodic system of elements instead of a limited range of expensive, inaccessible, often unstable alkoxides (alcoholates) of metals;

4) to obtain active silicate catalysts with one or more metals uniformly distributed in the silicate matrix from a wide range of elements.

The invention is illustrated by the following examples.

EXAMPLE 1. 2.67 g (0.02 M) of aluminum chloride, AlCl ₃ are gradually loaded into 30 ml of ethyl alcohol with stirring, and after dissolution 60 g of ethyl silicate-40 (0.40 M SiO ₂ ) are added. The resulting mixture is stirred at 35-50 ° C for 10-15 minutes until a clear solution is formed. 30 ml of ammonia water containing 70 mmol of ammonia are poured into the resulting solution with stirring, the resulting gel is dried in an oven for 4 hours at 150 ° C. The dried xerogel is ground and, raising the temperature at 2.5 ° C / min, calcined at a temperature of 550 ° C for 4 hours. In this case, water, ammonium chloride and alcohol residues disappear. Get 25 g of aluminosilicate catalyst with an atomic ratio of 100 Si: 5 Al, the properties of which are presented in table 1.

The phase composition of the sample was determined by X-ray diffraction on a PHILIPS-PW-1800 automatic diffractometer. The sample is a mesoporous material (figure 1).

The porous structure of the catalyst was investigated by measuring nitrogen adsorption-desorption isotherms at 77.4 K using a ASAP-2020 Micromeritics bulk vacuum static apparatus. The range of equilibrium relative pressures ranged from 10 ^-6 to 0.996 P / P ₀ . Analysis of the pore size distribution curve showed a wide distribution of mesopores in the region from 3 to 50 nm (FIG. 2).

EXAMPLE 2. In 20 ml of ethyl alcohol at 20 ° C and stirring, dissolve 1.5 g (0.004 M) of aluminum nitrate, Al (NO ₃ ) ₃ × 9H ₂ O, and after dissolution, 60 g of ethyl silicate-40 (0.4 M SiO ₂ ). 30 ml of ammonia water containing 15 mmol of ammonia are poured into the resulting solution with stirring. The resulting gel is dried in an oven for 5 hours at 150 ° C. The dried xerogel is ground and, raising the temperature at 2.6 ° C / min, calcined at a temperature of 550 ° C for 4 hours. In this case, ammonium nitrate decomposes, and water and alcohol residues evaporate. Get 24.1 g of aluminosilicate catalyst with an atomic ratio of 100 Si-Al, the properties of which are presented in table 1.

EXAMPLE 3. In 140 ml of ethanol load 64.5 g (0.20 M) of zirconyl chloride, ZrOCl ₂ × 8H ₂ O, and dissolved at 40-50 ° C. 60 g of ethyl silicate-40 (0.40 M SiO ₂ ) heated to 40-50 ° C are poured into an alcohol solution of zirconyl chloride, then with stirring 60 ml of ammonia water containing 450 mmol of ammonia. The resulting mass is dried in an oven for 6 hours at 100 ° C. The dried xerogel is ground, then, raising the temperature at a rate of 3 ° C / min, heated to 650 ° C and calcined for 6 hours. In this case, water, ammonium chloride and alcohol residues disappear. Get 48.4 g of zirconium silicate catalyst with an atomic ratio of 100 Si: 50 Zr, the properties of which are presented in table 1.

EXAMPLE 4. In 80 ml of ethyl alcohol, 8.6 g (0.027 M) of zirconyl chloride, ZrOCl ₂ × 8H ₂ O are charged and dissolved at 40-50 ° C. 60 g of ethyl silicate-40 (0.40 M SiO ₂ ) are poured into an alcohol solution of zirconyl chloride and then with stirring 30 ml of ammonia water containing 60 mmol of ammonia. The resulting mass is dried for 6 hours at 150 ° C. The dried xerogel is ground, then, raising the temperature at a rate of 3 ° C / min, heated to 500 ° C and calcined for 6 hours. In this case, water, ammonium chloride and alcohol residues disappear. Obtain 27.6 g of zirconium silicate catalyst with an atomic ratio of 100 Si: 6.7 Zr, the properties of which are presented in table 1.

EXAMPLE 5. In 20 ml of ethyl alcohol, 4.3 g (0.013 M) of zirconyl chloride, ZrOCl ₂ × 8H ₂ O are charged and dissolved at 40-50 ° C. 60 g of ethyl silicate-40 (0.40 M SiO ₂ ) heated to 40-50 ° C are loaded into an alcoholic solution of zirconyl chloride and then, with stirring, 0.82 g (0.006 M) of aluminum chloride, AlCl ₃ . 30 ml of ammonia water containing 52 mmol of ammonia are poured into the resulting solution with stirring. The resulting mass is dried for 5 hours at 150 ° C and, raising the temperature at a rate of 5 ° C / min, heated to 550 ° C and calcined for 4 hours. Obtain 26.0 g of aluminosirconium silicate catalyst with an atomic ratio of 100 Si: 3.3 Zr: 1.5 Al, the properties of which are presented in table 1.

EXAMPLE 6. 2.9 g (0.0067 M) of cerium nitrate, Ce (NO ₃ ) ₃ × 6H ₂ O, are dissolved in 100 ml of ethyl alcohol, at a temperature of 40-50 ° C. and with stirring, and then another 8.6 g (0.026 M) zirconyl chloride, ZrOCl ₂ × 8H ₂ O. First, 60 g of ethyl silicate-40 (0.40 M SiO ₂ ) are added to the resulting solution, and after stirring, 40 ml of ammonia water containing 80 mmol of ammonia. The resulting mass is dried for 5 hours at 150 ° C and, raising the temperature at a rate of 4 ° C / min, heated to 550 ° C and calcined for 4 hours. In this case, water, ammonium chloride, alcohol residues and decomposition products of ammonium nitrate evaporate. Obtain 28.4 g of zirconium cerium silicate catalyst with a ratio of 100 Si: 6.6 Zr: 1.67 Ce, the properties of which are presented in table 1.

EXAMPLE 7. 20 ml of ethyl alcohol are poured into 45 g of ethyl silicate-40 (0.30 M SiO ₂ ) and with stirring 1.1 ml (1.9 g; 0.01 M Ti) of titanium tetrachloride, TiCl ₄ . Then with stirring, 20 ml of ammonia water containing 45 mmol of ammonia are added. The resulting mass is dried for 5 hours at 150 ° C and, raising the temperature at a rate of 2 ° C / min, heated to 550 ° C and calcined for 4 hours. Obtain 18.8 g of a titanium silicate catalyst with an atomic ratio of 100 Si: 3.3 Ti, the properties of which are presented in table 1.

EXAMPLE 8. 2.45 g (0.01 M) of manganese acetate, (CH ₃ COO) ₂ Mn × 4H ₂ O are dissolved in 25 ml of ethyl alcohol, 45 g of ethyl silicate-40 (0.30 M SiO ₂ ) are added with stirring. and then 15 ml of ammonia water containing 35 mmol of ammonia. The resulting mass is dried for 5 hours at 150 ° C and, raising the temperature at a rate of 4 ° C / min, heated to 550 ° C and calcined for 4 hours. Obtain 19.0 g of manganese silicate catalyst with an atomic ratio of 100 Si: 3.3 Mn, the properties of which are presented in table 1.

EXAMPLE 9. 2.7 g (0.0067 M) of iron nitrate, Fe (NO ₃ ) ₃ × 9H ₂ O are dissolved in 25 ml of ethyl alcohol, 30 g of ethyl silicate-40 (0.20 M SiO ₂ ) are poured, stirred and poured 20 ml of ammonia water containing 30 mmol of ammonia. The resulting mass is dried for 5 hours at 150 ° C and, raising the temperature at a rate of 4 ° C / min, heated to 550 ° C and calcined for 4 hours. Get 12.5 g of iron-silicate catalyst with an atomic ratio of 100 Si: 3.3 Fe, the properties of which are presented in table 1.

The catalytic activity of the synthesized elemental silicates was investigated in the dimerization of α-methylstyrene:

3 ml (2.65 g) of α-methylstyrene, 0.13 g (5% by weight of α-methylstyrene) of the catalyst were loaded into a glass heated reactor with a stirrer, reflux condenser and thermometer and stirred in a water bath for 1 hour at a temperature 96 ° C. After cooling and filtering off the catalyst, the composition of the reaction mixture was determined using gas-liquid chromatography. Data on the catalytic activity of the obtained samples are presented in table 2.

Table 1 Physical Characteristics of Mesoporous Amorphous Mixed Elementosilicates Silicate Atomic ratio of elements Bulk density, g / cm ³ Specific surface, m ² / g The pore volume in pairs of benzene, cm ³ / g The pore volume of water vapor, cm ³ / g as in example 1 100Si: 5Al 0.38 395 1.06 0.05 as in example 2 100Si: Al 0.29 275 0.92 0,03 as in example 3 100Si: 50Zr 0.94 202 0.18 0,07 as in example 4 100Si: 6.7Zr 0.49 600 0.58 0.15 as in example 5 100Si: 3.3Zr: 1.5Al 0.48 450 0.37 0.05 as in example 6 100Si: 6.6Zr: 1.67Ce 0.52 482 0.67 0.06 as in example 7 100Si: 3.3Ti 0.51 368 0.63 0,07 as in example 8 100Si: 3.3Mn 0.44 487 0.84 0.10 as in example 9 100Si: 3.3Fe 0.63 246 0.48 0,07

table 2 Dimerization of α-methylstyrene in the presence of mesoporous amorphous mixed elementosilicates Silicate The conversion of α-methylstyrene,% The composition of the dimerization products of α-methylstyrene,% α-methyl styrene cyclic dimer (1) linear dimers (2 a, b) trimers as in example 1 96.9 3,1 15.4 73.7 7.8 as in example 2 85.0 15.0 4.8 72,2 8.0 as in example 3 93.7 6.3 17.5 68.3 7.9 as in example 4 35.8 4.2 16,0 66.8 13.0 as in example 5 99.0 1,0 30,0 54.3 14.7 as in example 6 95.0 5,0 12.3 71,4 11.3 as in example 7 92.0 8.0 23.9 62,4 5.7 as in example 8 95.0 5,0 11,4 71.9 11.7 as in example 9 90.2 9.8 19.8 61,4 9.0

Claims (5)

1. A method of producing mesoporous amorphous mixed elementosilicates, comprising preparing a xerogel, characterized in that the xerogel is obtained by treating a solution obtained by mixing salts of one or more metals (Me) with ethyl silicate 40, aqueous ammonia, and then drying the resulting paste in air under atmospheric pressure at 100-150 ° C for 4-6 hours, then the xerogel is calcined at 500-650 ° C for 4-6 hours and ground. 2. The method according to claim 1, characterized in that, as metal salts, chlorides, nitrates, acetates Al, Ti, Fe, Zr, Sn, Ca, Cu, Mn, Cr and other metals are soluble in ethanol or other organic solvents. 3. The method according to claim 1, characterized in that the atomic ratio of Si: Me in the initial mixture varies in the range from 100: 1 to 2: 1. 4. The method according to claim 1, characterized in that the treatment of the initial solution of a metal salt of ethyl silicate-40 is carried out with an aqueous ammonia solution containing 1 ± 0.1 equivalent of ammonia per salt equivalent and 30 mmol of ammonia per 100 g of ethyl silicate-40. 5. The method according to claim 1, characterized in that when calcining the xerogel, the temperature is raised to 500-650 ° C at a speed of 2-5 ° C / min.

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