CS257251B2 - A method for producing aluminum-modified silica - Google Patents

Abstract

The process for producing aluminum-modified silica with a porous crystalline structure, a specific surface area greater than 150 m^/g, of the general formula Si . (0.001 2 to 0.005 0) AI . Oy in which y ranges from 2.001 8 to 2.007 5, and with a molar ratio of silica to alumina ranging from 38 to 816, is carried out by reacting a silicon compound with an aluminum compound in the presence of a clathrate-forming agent and optionally in the presence of a mineralizing agent and an inorganic basic compound. The mixture is allowed to crystallize in a closed environment for 5 to 20 days at a temperature of 100 to 220 °C, after which it is filtered, dried and calcined, optionally washed and calcined again. The obtained substances can be used as catalysts for various reactions, especially alkylations.

Description

The invention relates to a method for producing aluminum-modified silica with a porous 2-crystalline structure, with a specific surface area greater than 150 m/g and with a molar ratio of SiO2:A2O2 in the range from 38 to 816.

As far as the prior art is concerned, a large number of substances based on silicon dioxide and alumina are known, some of which occur in nature and others are produced artificially.

The group of these substances also includes substances generally referred to as zeolites, which are suitable as adsorbents and molecular sieves, and these substances have good catalytic properties.

The alumina content of these materials in relation to silica varies widely. The maximum ratio of silica to alumina is 100:1, but this ratio is usually much lower, preferably around 2.

In order for these materials, which contain aluminum in a tetrahedral configuration as a substitute for silicon, to be electrically neutral, they must contain cations capable of balancing the charges resulting from the presence of aluminum atoms arranged in said tetrahedral configuration.

The protonic acidity of these zeolites can be derived from the hydrogen atoms that have been introduced as a replacement for the aforementioned cations. On the other hand, crystalline silicas, due to their intrinsic character, do not contain protonic charges and therefore cannot exhibit an acidic character that is not related to silicic acid.

According to the prior art, many different types of crystalline silica are known and used, from cristobalite to tridymite and keatite, and in addition many other substances prepared by processes that are described in detail in the technical literature. For example, according to Heidemann, see Beitr. Min. Petrog. 10, 242 (1964), it is possible to obtain by reacting amorphous silica with 0.55% by weight of potassium hydroxide at a temperature of 180 ° C for two and a half days, crystalline silica, called silica X, which has a specific surface area of about 10 m /g and low stability, since it passes into cristobalite and then into quartz within five days. Flanigen et al. reports in Nature, 271, 512 (1978), a process for obtaining crystalline silica, referred to as silicalite, with a large specific surface area, and due to its hydrophobic nature, the use of this material for the purification of water polluted with organic substances was proposed.

The aim of the present invention is to propose a process for preparing crystalline silicon dioxide modified with aluminum while maintaining the unchanged stability of silicon dioxide and thus to prepare a substance that would be suitable as a catalyst or as a starting material for the preparation of a catalyst.

Another aim of the invention is to develop a process for preparing silicon dioxide modified by introducing aluminum atoms, which would exhibit acidity and catalytic activity suitable for certain reactions.

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The essence of the method for producing aluminum-modified silica with a porous crystalline 2 structure, with a specific surface area greater than 150 m /g and with a molar ratio of SiO^iAl^O^ in the range from 38 to 816, which corresponds to the general formula

Si . (0.001 2 to 0.005 0) Al . 0 _y in which y ranges from 2.001 8 to 2.007 5, according to the invention, consists in reacting a silicon compound from the group comprising silicon dioxide and tetraalkyl orthosilicates with an aluminium compound, such as aluminium nitrate and aluminium acetate, in an aqueous, alcoholic or aqueous-alcoholic solution in the presence of a clathrate-forming reagent from the group comprising tertiary amines, amino alcohols and tetraalkyl ammonium hydroxides which contain 1 to 5 carbon atoms in the alkyl part, and triethanolamine, optionally adding one or more mineralising agents and optionally an inorganic basic compound.

The mixture is allowed to crystallize in a closed environment for 5 to 20 days at a temperature ranging from 100 to 220 °C, after which it is allowed to cool and, after filtration and drying, it is calcined in air at a temperature ranging from 300 to 700 °C for 2 to 24 hours, optionally washed with boiling distilled water containing ammonium salt, and calcined again under the above conditions.

According to the present invention, it has been unexpectedly found that it is possible to prepare materials with a high molar ratio of silica to alumina, which are not zeolites, since the minimal amount of aluminium contained therein cannot provide a crystalline aluminosilicate structure.

On the other hand, these materials obtained by the process according to the invention are completely different from crystalline silicas in that the introduction of a small amount of aluminum results in large changes in acidity.

The materials obtained by the process according to the invention have a protonic acidity equal to or greater than that of the protonic forms of zeolites and at the same time retain a very high structural stability of crystalline silica, which is the opposite trend to that observed in the protonic forms of zeolites A, X and Y (with the sole exception of the mordenite group), which are relatively labile and tend to easily convert to more stable mixtures of silica and alumina.

Mixtures of silica and alumina as such have somewhat lower acidity, for example a commercially available mixture of silica and alumina (silica-alumina) containing 25% by weight of alumina has a concentration of the order of 1.10 meq. H per gram of catalyst.

Furthermore, according to the invention, it has been found that, quite surprisingly, by appropriately dosing the amount of aluminum in the final product, the acidity of this product can be adjusted so that it is adapted to a specific requirement, which is given by the type of reaction carried out for which the given material is intended.

In a preferred embodiment of the present invention, the tetraalkyl orthosilicate is tetraethyl orthosilicate and tetramethyl orthosilicate, and the preferred mineralizing agent is an alkali metal or alkaline earth metal halide selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, potassium bromide, sodium bromide, sodium iodide, calcium iodide or calcium bromide. The inorganic base used in the preferred embodiment of the process according to the present invention is an alkali metal hydroxide and/or alkaline earth metal hydroxide and/or ammonia, with the most preferred alkali metal hydroxides and alkaline earth metal hydroxides being sodium hydroxide, potassium hydroxide and calcium hydroxide.

In a preferred embodiment of the process according to the invention, the amount of inorganic base and/or tetraalkylammonium hydroxide or triethanolamine is less than the stoichiometric amount based on silicon dioxide, and this amount is preferably 0.05 to 0.50 mole per mole of silicon dioxide.

According to the invention, the silica modified by the introduction of aluminum atoms has the general formula:

Si . (0.001 2 to 0.005 0) Al . 0 in which y ranges from 2.001 8 to 2.007 5. Depending on the calcination temperature, a greater or lesser amount of crystal water may be present.

The following procedure can generally be used to obtain the aluminum-modified silica according to the invention. The silicon derivative and the aluminum derivative are reacted in an aqueous, alcoholic or aqueous-alcoholic solution with a substance acting as a clathrate or archivolt, optionally one or more mineralizing agents are added to promote crystallization and optionally an inorganic basic compound. The mixture obtained is allowed to crystallize in a closed environment for a period of time, which can generally range from several hours to many days, at a temperature in the range of 100 to 220 ° C, in a preferred embodiment in the range of 150 to 200 ° C for a period of one week. The obtained product is then allowed to cool and, after filtration, dried and calcined at a temperature in the range of 300 to 700 ° C, in a preferred embodiment according to the invention this temperature is about 550 ° C, for a period of time in the range of 2 to 24 hours. This is followed by washing to remove any ion-exchangeable cationic impurities present with boiling distilled water containing dissolved ammonium salt, whereby nitrate or acetate can also be advantageously used, and then the above-mentioned calcination can be repeated.

The silicon derivatives may be selected from the group consisting of any silicon dioxide-based material, for example silica gel (regardless of its preparation method) and tetraalkyl orthosilicates, such as tetraethyl orthosilicate and tetramethyl orthosilicate.

The aluminum derivatives may preferably be selected from the group comprising aluminum salts, for example aluminum nitrate or aluminum ootane.

Substances with clathrate-forming activity can be selected from the group comprising tertiary amines, amino alcohols, amino acids, polyalcohols and quaternary ammonium bases, such as tetraalkylammonium bases of the general formula NR^OH, where R is an alkyl containing 1 to 5 carbon atoms or tetraarylammonium bases of the general formula NA^OH, where A is a phenyl or alkylphenyl radical.

The task of clathrate-forming substances is to contribute to the desired crystal structure with pores of a defined size, and therefore these substances are formed by molecules of the corresponding size.

The products obtained according to the invention are characterized by a protonic type acidity, which can be adjusted by changing the introduced substituting cation. For pure silica, the number of milliequivalents of hydrogen ions per gram of sample is 1.10, and this acidity can be increased by introducing aluminum atoms up to a value of about 1.10 milliequivalents of hydrogen ions per gram of sample.

The materials obtained by the process according to the invention are also notable for their defined crystalline structure, as will be further apparent from the attached X-ray diffraction patterns shown in Figs. 1 and 2, and these materials have a large specific surface area exceeding 150 m2/g and typically reaching values of 300 to 500 m2/g.

The presence of aluminum, which so strongly modifies the acidity of silica, favorably affects the formation of crystalline materials whose spectra either strongly resemble those reported in the literature for crystalline silica, called silicalite (Nature, 271, 512 (1978)) or, conversely, differ significantly from them.

The alumina-modified silica obtained by the process according to the invention can be used for catalytic or adsorption purposes either as such or dispersed on a support, more or less inert, which may have a large or small specific surface area and porosity.

The purpose of the support material is to increase the physical stability and mechanical resistance and possibly the catalytic properties of the material. Any of the known methods can be used for the preparation of substances deposited on the support.

The amount of carrier material in the final product may range from 1 to 90%, preferably from 5 to 60% by weight.

Examples of suitable carriers include clays, silica, alumina, diatomaceous earth, a mixture of silica and alumina, and other materials.

The aluminum-modified silica obtained by the process according to the present invention can be advantageously used as a catalyst for a large number of diverse reactions, for example advantageously for the alkylation of benzene, in particular the alkylation of benzene with ethylene and the alkylation of benzene with ethanol.

Other possible reactions include the following:

- alkylation of toluene with methanol to xylene, mainly to p-xylene,

- disproportionation of toluene to form mainly p-xylene,

- conversion of dimethyl ether and/or methanol or other (lower) alcohols to hydrocarbons, such as olefins and aromatics,

- cracking and hydrocracking,

- isomerization of normal paraffins and naphthenes,

- polymerization of compounds containing olefinic or acetylenic bonds,

- reforming,

- isomerization of polyalkyl-substituted aromatics such as o-xylene,

- disproportionation of aromatics, especially toluene,

- conversion of aliphatic carbonyl compounds into at least partially aromatic hydrocarbons,

- separation of ethylbenzene from other C _g aromatic hydrocarbons, ¹

- hydrogenation and dehydrogenation of hydrocarbons,

- methanization.

In the accompanying figures, which relate to the following examples, Fig. 1 is an X-ray diffraction pattern of the product obtained by the process according to Example 4, while Fig. 2 is an X-ray diffraction pattern of the product obtained by the process according to Example 6.

In the following, several examples of practical implementation of the process according to the invention will be given, the purpose of which is to illustrate this process in more detail without limiting it in any way. »

Example

This example will illustrate the process of preparing porous crystalline silica, in which aluminum has been introduced into the crystal lattice as a substitute for silicon, and the product is designated TRS-22.

In a glass vessel (made of Pyrex glass), which was kept under a constant nitrogen atmosphere, 80 grams of tetraethyl orthosilicate (TEOS) were placed, which was heated to a temperature of 80 ° C while stirring. Then, a solution of 20 grams of tetrapropylammonium hydroxide (obtained from tetrapropylammonium and moistened silver oxide in order to obtain a product free of inorganic alkaline basic substances) in 80 milliliters of distilled water was added, the mixture being stirred at a temperature of 80 ° C until a homogeneous and clear mixture was obtained, which took about 1 hour.

After this addition, a compact gel was formed almost immediately, to which distilled water was added to a total volume of 200 milliliters, then stirring was used if necessary, and then the mixture was brought to a boil in order to complete the hydrolysis and distill off all the ethanol, i.e. both added and released by hydrolysis.

These phases took place over a period of 2 to 3 hours, with the gel slowly gradually turning into a white powder, which was a precursor to the modified crystalline silica.

This mixture was then made up to 150 milliliters with distilled water and the glass container was then placed in an autoclave and left there for 7 days at 155°C. After cooling, the resulting solid was centrifuged at 10,000 ^{rpm for} 15 minutes, resuspended in distilled water and then centrifuged again, and this washing step was repeated four times in total. The product obtained was then dried in a drying device at 120°C and was found to be X-ray crystalline.

Chemical analysis of the obtained product, dried at 120 °C, revealed the following composition:

SiO ₂ ai ₂ o ₃ Na ₂ 0 99.52% by weight 0.24% by weight 0.22% by weight to ₂ o 0.02% by weight

The chemical formula of the product is: 1 Si . /0.002 8/ Al . 0^. The loss on ignition of this product at 1100 °C was 16.6%, with a molar ratio of SiO ₂ :Al ₂ O ₃ of 704.

The alkali metals present in the final product were derived from the reactants and the glass, as they were not added separately. In cases where it is necessary to remove the alkaline impurities present, the material can be annealed for 16 hours at 550 °C in a stream of air, then repeatedly washed with boiling distilled water containing dissolved ammonium acetate, and then annealed again for 6 hours at 550 °C.

The specific surface area determined by the BET method was 444 m/g, with the amount of protons per gram of sample corresponding to 1.5 . 10 ^-1 meq./g.

Example 2

This example will illustrate the process of preparing porous crystalline silica, designated TRS-O, into whose crystal lattice traces of aluminum have been introduced as a substitute for silicon.

In a glass vessel (made of Pyrex glass) equipped with a reflux condenser and maintained under a nitrogen atmosphere, 40 grams of tetraethyl orthosilicate (TEOS) and 120 milliliters of a 20% (w/w) aqueous solution of tetrapropylammonium hydroxide were placed, and the resulting mixture was heated to boiling. In this way, a translucent colorless solution was obtained, which remained clear even after prolonged reflux.

Then 30 milligrams of aluminum nitrate Al(NO ₃ > ₃ . 9 HjO were added and the liquid turned to an opalescent appearance, with a white powder separating on continued heating.

Heating at reflux was carried out for 6 days, after which the mixture was allowed to cool, the solid was separated on a filter and washed with distilled water and dried at 100°C.

The product dried at 100°C was X-ray crystalline. This product was calcined for 16 hours at 550°C in a stream of air and then repeatedly washed with boiling distilled water containing dissolved ammonium acetate, after which the solid was calcined once more at 550°C for 6 hours.

Chemical analysis of the product thus obtained revealed the following composition:

SiO _n

99.78% by weight 0.20% by weight 0.02% by weight

The general formula of this product is: 1 Si . /0.002 4/ AI . O _y .

The loss on ignition at 1,100 °C was 3.58% by weight, with a molar ratio of SiO ₂ :Al ₂ O ₃ of 816.

Trace amounts of alkali metals present in this product were derived from the reactants and glass, as these were not added separately. The specific surface area, determined by the BET method, was 420 m2/g, with a proton concentration per gram of sample of 1.9 x 10 ^-1 meq/g.

Example 3

This example will illustrate the process of preparing porous crystalline silica designated TRS-23, into the crystal lattice of which aluminum was introduced as a substitute for silicon, and in this process a different organic basic compound was used than in Examples 1 and 2, namely tetraethylammonium hydroxide.

In this procedure, in the same way as in Example 1, 80 grams of tetraethyl orthosilicate, 68 milliliters of an aqueous solution of tetraethylammonium hydroxide with a concentration of 25% by weight, 80 milligrams of aluminum nitrate A1(NO ₃ > ₃ . 9 H ₂ O, which was dissolved in 50 milliliters of absolute ethanol, and 2 grams of sodium hydroxide pellets, which was dissolved in 10 milliliters of distilled water, were added to the reaction, and the mixture was left at a temperature of 155 °C for 18 days.

The product thus obtained was X-ray crystalline after drying at 120° C. The proton concentration per gram of the sample (annealed at 550° C. for 4 hours) corresponded to 1.1 x 10 & meq./g.

Chemical analysis of a carefully washed sample, which was calcined at 550 °C for 4 hours, revealed the following composition:

_SiO2 99.77% by weight

AlO 0.20% by weight

Na ₂ O 0.03% by weight

The general formula of the product is: 1 Si . /0.002 4/ AI . About .

The loss on ignition at 1100 °C corresponded to 3.47% by weight, with the molar ratio of this product being: _SiO2 : _Al2O3 = _816. The specific surface area determined by the BET method was 470 ^m2 /g and the proton concentration per gram of sample was 4.3. ^Í0-3 meq/g.

Example 4

This example will illustrate the process of preparing porous crystalline silica designated TRS-19, into the crystal lattice of which aluminum was introduced as a substitute for silicon, and tetrabutylammonium hydroxide was used as the organic base in this preparation.

In this example, the same procedure was followed as in Example 1, with 50 grams of tetraethyl orthosilicate (TEOS), a solution of 100 milligrams of aluminum nitrate Al(NO ₃ ) ₃ . 9 H ₂ O in 50 milliliters of absolute ethanol, a solution of 29 grams of tetrabutylammonium hydroxide (obtained from tetrabutylammonium bromide and wetted silver oxide) in 120 milliliters of distilled water, and 2 grams of sodium hydroxide dissolved in 20 milliliters of distilled water.

This mixture was placed in an autoclave and left there for 16 days at a temperature of 155 °C.

The product thus obtained, dried at 120°C, was X-ray crystalline.

The proton concentration per gram of the sample (annealed at 550 °C for 5 hours) was

-d

4.5 . 10 meq./g.

Chemical analysis of a carefully washed sample revealed the following composition:

SiO ₂ 99.66% by weight

AûjOg 0.31% by weight

At ₂ 0 0.03% by weight

The general formula of the product is: 1 Si . (0.003 6) . AI . O 'The loss on ignition at a temperature of 1 100 °C for this product was 3.67% by weight, the molar ratio of SiO ₂ : Al ₂ Oj was 543, the specific surface area determined by the BET method was 380 m /g and the concentration of protols per gram of sample corresponded to 2.5 . 10 ³ meq./g.

The attached Fig. 1 shows the X-ray diffraction pattern of the products obtained by the process according to this example.

Example 5

In this embodiment example, the preparation process of porous crystalline silicon dioxide with the designation TRS-20 will be illustrated, into the crystal lattice of which aluminum was introduced as a substitute for silicon, and the preparation of this product was carried out without the presence of an inorganic alkaline basic compound, i.e. the only possibility of the presence of alkaline cations is from trace impurities that are present in the reagents used.

In this example, the same procedure was followed as in Example 1, whereby 40 grams of tetraethyl orthosilicate, a solution of 100 milligrams of aluminum nitrate A1(NO ₃ ) ₃ . 9 H ₂ O in 50 milliliters of absolute ethanol, 50 milliliters of an aqueous solution of tetrapropylammonium hydroxide with a concentration of 40% by weight (obtained from tetrapropylammonium bromide and wetted silver oxide) were added to the reaction, the purpose being to obtain a product free of alkaline inorganic bases, and the mixture was left for 10 days at a temperature of 155 °C.

The sample dried at 120 °C was X-ray crystalline.

When used as a catalyst, this product was calcined for 16 hours in air at 550°C and then repeatedly washed with boiling distilled water containing dissolved ammonium acetate, and finally the solid was calcined again for 6 hours at 550°C.

The product thus obtained was analyzed for its chemical composition, which was as follows:

SiO ₂ 99.68% by weight

AlO 0.31% by weight

Na ₂ O 0.01% by weight

The general formula of the product is: 1 si . /0.003 6/Ά1 . O^.

The loss on ignition at 1100 °C was 3.59% by weight for this product, the molar ratio of _SiO2 : _Al2O3 was _544. The specific surface area determined by the BET method was 500 ^m2 /g and the concentration of H ⁺ cations per gram of sample was ^4.7.10-1 meq/g.

Example 6

This example will illustrate the process of preparing porous crystalline silica designated TRS-57, into the crystal lattice of which aluminum was introduced as a substitute for silicon, and triethanolamine was used in this preparation.

In this example, the procedure was the same as in Example 1, with 80 grams of tetraethyl orthosilicate, 80 milligrams of aluminum nitrate Al(NO ₃ > ₃ . 9 H ₂ O, which was dissolved in 50 milliliters of absolute ethanol, and a solution of 27 grams of triethanolamine in 50 milliliters of distilled water being added to the reaction. Then 7 grams of sodium hydroxide were added, and the glass container (made of Pyrex glass) was placed in an autoclave and left there for 7 days at a temperature of 194 °C.

The product thus obtained, dried at 120 °C, was X-ray crystalline. The X-ray diffraction pattern of this product is shown in the attached Fig. 2.

Chemical analysis of the product thus obtained, which was calcined at 550 °C for 4 hours, revealed the following composition:

SiO ₂ 99.74% by weight

AlO 0.21% by weight

Na ₂ O 0.05% by weight

The general formula of the product is: 1 Si . /0.002 4/ AI . Oy.

/

The loss on ignition at 1100 °C for this product was 3.55 % by weight, the molar ratio of _SiO2 : _Al2O3 was 816, the specific surface area determined by the BET method was 344 m2/ _g , and the concentration of H ⁺ cations per gram of sample was 1.5. ^10-10 meq/g.

In the following examples, practical possibilities of using aluminum-modified silica obtained by the process according to the invention for various reactions will be illustrated.

Example 7

First, in this first example, concerning the use of materials obtained by the process according to the invention, the unusability of sodium-modified silica, which is therefore not within the scope of the invention, for dehydration purposes will be illustrated. In this embodiment, the modified silica designated TRS-22 (see Example 1) was used as the catalyst, but modified with sodium cations, so that the proton concentration of this product -4 was only 4.1 . 10 meq./g of sample.

The preparation of dimethyl ether from methanol was chosen as an example of a dehydration reaction. 4 milliliters (i.e. 2 grams) of a catalyst fraction with particle sizes ranging from 600 to 180 μm were introduced into an electrically heated tubular reactor with an internal diameter of 8 millimeters. The sample emerging from the reactor was analyzed by gas chromatography.

The catalyst used was first annealed in a nitrogen stream at 500°C for 2 hours to remove absorbed water. Methanol was then fed at a mass space velocity for 1.5 hours at a reactor temperature of 275°C and then at a reactor temperature of 400°C.

Analysis of the reactor outlet stream confirmed the presence of only methanol at both temperatures.

Examples

This example serves as a comparative example, illustrating the unusability of aluminum-modified silica, designated TRS-23 (see Example 3), carelessly washed so that the proton concentration was only 1.1 × ^10-10 meq/g of sample, for dehydration purposes.

In this example, the same procedure as in Example 7 was followed, with 4 milliliters (i.e. 2.8 grams) of catalyst with a particle size ranging from 600 to 180 µm being introduced into the reactor, and the catalyst being heated at 500°C for 2 hours in a stream of anhydrous nitrogen.

Methanol was then added at temperatures of 240, 300 and 400 °C at a mass space velocity of 1.75 h ^-1 . In all three cases, no dimethyl ether was detected in the reactor effluent, only methanol was detected.

Example 9

This example will illustrate the excellent catalytic dehydration properties of a modified crystalline silica designated TRS-22, prepared according to the procedure of Example 1, in which the proton concentration was 1.5 x 10 ¹ meq/g of sample.

The procedure was the same as in Example 7, with 5 milliliters (i.e. 3.5 grams) of a catalyst fraction with a particle size ranging from 600 to 180 μm being charged to the reactor. The catalyst was annealed for 2 hours in a stream of anhydrous nitrogen to remove absorbed water, after which methanol was fed at a mass space velocity of 1.5 h ¹ and at reactor temperatures of 250 and 265 °C.

Analysis of the outlet stream from this reactor, which consisted of dimethyl ether, unreacted methanol and water, with no by-products detectable by gas chromatography, yielded the values shown in Table 1 below.

From the results given, it is clear that the crystalline silica prepared by the process according to the invention, i.e. modified with aluminum, has excellent dehydration efficiency, with conversion values being higher than in the process with active alumina that has been modified with silicon compounds.

As evidence, it can be stated that when using the aluminum-modified silica catalyst according to the invention, designated TRS-22, a methanol conversion is achieved at temperatures of 250 and 265 °C and a mass space velocity of 1.5 h ^-3 which is the same or higher than the conversion achieved at a temperature of 300 °C and a mass space velocity of 1 h ³ using active alumina that has been modified with silicon compounds.

Table No. 1

Dehydration of methanol to dimethyl ether

Catalyst: TRS-22 prepared according to the procedure of Example 1

Temperature 250°C 265°C pressure (MPa) 0.1 0.1 mass space velocity (h ^-1 ) 1.5 1.5 methanol conversion (% molar) 82.4 88.1

Example 10

This example is comparative. In this example, a process for converting dimethyl ether to hydrocarbons, with special emphasis on light olefins, will be illustrated using a modified crystalline silica designated TRS-22, prepared according to the procedure of Examples 1 and . -4 containing sodium cations, such that the proton concentration was only 4.1 . 10 meq/g catalyst.

An electrically heated tubular reactor with an internal diameter of 8 millimeters was loaded with 2 millimeters (i.e., 1 gram) of catalyst with a particle size ranging from 600 to 180 μm. The catalyst was first heated for 2 hours at 550°C in a nitrogen stream to remove any adsorbed water present. Dimethyl ether gas was fed through a heated line to prevent condensation. A suitable heated sampling device was placed downstream of the reactor to allow the reactor effluent to be fed to a gas chromatograph in which a complete analysis of the reaction products was performed.

Regarding the calculation of conversion, it should be noted that methanol formed by partial hydration of dimethyl ether is considered an unreacted product, so the molar conversion only applies to dimethyl ether that has been converted to hydrocarbons and carbon monoxide and carbon dioxide.

The molar selectivity of the products under consideration is the number of moles of dimethyl ether that have been converted to the said product, relative to the total number of moles reacted.

The results obtained in carrying out this procedure are shown in Table 2, from which it is clearly evident that the tested catalyst is neither very active nor very selective, which is evident from the fact that a significant amount of carbon monoxide, carbon dioxide and methane was produced.

Table No. 2

Conversion of dimethyl ether to hydrocarbons

Catalyst: TRS-22 containing sodium cations

Attempt number Temperature (°C) Pressure (MPa) Space velocity (h ^_1 ) Conversion in one pass (% molar) Selectivity for individual products CO + CO ₂ + (% molar) ch ₄ c ₂ h ₄ ^{C3H6 ​ C} 4 1 375 0.1 0.65 2.3 ' 5.0 14.9 30.1 50.0 2 475 0.1 0.20 97.0 10.9 6.5 26.1 56.5

Example 11

This example will illustrate the conversion of dimethyl ether to hydrocarbons with a particular focus on light olefins using a modified crystalline silica designated TRS-22, which was prepared according to the procedure of Example 1 and contained 1.5 x 10* meq protons per gram of sample.

In this example, the same procedure as in Example 9 was used, with 3 milliliters (1.5 grams) of catalyst with a particle size ranging from 600 to 180 µm being charged to the reactor. The catalyst was first heated at 550°C for 2 hours under a stream of nitrogen to remove adsorbed water.

The results obtained are shown in the following table 3. From the comparison with table 2 it is clear that the behavior of the catalyst improves with the change in acidity.

Table No. 3

Conversion of dimethyl ether to hydrocarbons

Catalyst: TRS-22

Attempt number Temperature <°C) Pressure (MPa) Space velocity (h- ¹ ) Conversion in one pass (mol%) Selectivity to the obtained products (% molar) CO + CO ₂ + ch ₄ c ₂ h ₄ ^{C3H6 ​ C} 4 1 305 0.1 2.7 38.8 0.5 30.1 24.3 45.1 2 335 0.1 2.7 87.9 0.5 23.0 19.9 56.6 3 365 0.1 4.7 97.3 0.5 19.0 18.8 61.7 4 365 0.1 6.7 87.4 0.5 23.2 19.7 56.6 5 485 0.1 6.7 97.1 0.5 18.3 18.7 61.9 6 485 0.1 8.7 87.1 0.5 20.1 18.2 61.2 7 440 0.1 9.0 92.1 0.5 16.5 15.2 67.8

Example 12

In this embodiment, the activity of the aluminum-modified silica catalyst TRS-22 ( ^1.5.103 meq. H ⁺ /g), see Example 1, in the alkylation of benzene with ethylene will be illustrated.

According to this embodiment, 1.2 milliliters (0.8 grams) of TRS-22 catalyst with a particle size ranging from 600 to 300 microns was placed in an electrically heated tubular reactor with an internal diameter of 8 millimeters. Benzene was fed by a metering pump first into a preheating system, where it was brought into contact with a pre-selected amount of ethylene and then this mixture was discharged into the reactor. The reaction products were analyzed by gas chromatography. The results obtained are shown in the following table No. 4.

Table No. 4

Alkylation of benzene with ethylene catalyst: TRS-22, pressure: 2 MPa, liquid phase space velocity: 14 h ³ , molar ratio C ₆ H ₆ :C ₂ H ₄ =7

Operating time (h) Temperature (°C) Amount of ethylbenzene in the product (% molar) Amount of diethylbenzene in the product (% molar) Ethylene conversion (%) 10 440 13.8 1.50 100.0 50 440 13.7 1.55 100.0 100 440 13.9 1.45 100.0 150 440 13.9 1.45 100.0 200 440 13.8 1.50 100.0 250 440 11.9 0.80 80.8 300 440 8.2 0.25 51.8 380 470 11.5 0.70 76.7 350 470 10.9 0.65 72.6 400 470 10.3 0.60 68.2

Example 13

In this example, the regeneration process of a used catalyst will be illustrated.

The same catalyst as in Example 12 (designated TRS-22 prepared according to the procedure of Example 1) was regenerated after 400 hours of operation, this regeneration being carried out for 5 hours at a temperature of 550 ° C in a suitably adjusted air flow. After the regeneration was completed, the system was purged with nitrogen for 1 hour, which was also carried out at a temperature of 550 ° C, and then the reaction was carried out again under the conditions given in Example 12.

The results obtained are shown in the following table No. 5.

Table No. 5

Alkylation of benzene with ethylene'

Catalyst: regenerated TRS-22, pressure: 2 MPa, liquid phase space velocity: 14 h ^-1 , molar ratio CgHg:C ₂ H^ =7

Operating time (h) Temperature (°C) Amount of ethylbenzene in the product (% molar) Amount of diethylbenzene in the product (% molar) Ethylene conversion (%) 10 440 13.7 1.55 100.0 50 440 13.6 1.40 97.6 100 440 13.8 1.50 100.0 150 440 13.9 1.45 100.0 200 440 13.7 1.55 100.0 250 440 12.2 0.95 ' 83.9 300 440 10.3 0.60 68.45 350 440 9.8 0.38 62.85

Example 14

In this working example, the activity of the aluminum-modified silica catalyst TRS-0 (see Example 2) in the alkylation of benzene with ethanol will be illustrated.

According to this embodiment, 1.2 milliliters (0.8 grams) of catalyst with a particle size ranging from 600 to 300 μm was placed in an electrically heated tubular reactor with an internal diameter of 8 millimeters. A reaction mixture consisting of benzene and ethanol in a molar ratio of 5:1 was fed by a metering pump, first to the preheater and then to the reactor.

The reaction was carried out at a temperature of 440 °C, and the reaction products were analyzed by gas chromatography. The results are shown in Table 6.

Table No. 6

Alkylation of benzene with ethanol catalyst: TRS-0, temperature: 440 °C, pressure: 2 MPa, liquid phase space velocity: 10 h ^- \ molar ratio CgHg:C ₂ HgOH = 4

Table No. 6 continued

Operating time (h) Amount of ethylbenzene in the product (% molar) Amount of diethylbenzene in the product (% molar) Conversion of C ₂ HgOH (%) 50 19.0 1.2 100 100 19.0 1.2 100 150 19.0 1.2 100 200 19.0 1.2. 100 300 19.0 1.2 100 400 19.0 1.2 100

Example 15

According to this example, 5 milliliters of aluminum-modified silica with the designation TRS-0, prepared according to the procedure of Example 5, were impregnated with an aqueous solution of hexachloroplatinic acid H ₂ PtCl 8 so that the platinum content in the catalyst was 0.2% by weight.

Platinum was reduced to elemental form at 600°C in a stream of hydrogen, after which the material was transferred to an electrically heated tubular reactor with an internal diameter of 20 millimeters.

The capacity to remove automobile exhaust gases was tested on two typical reactions, namely the oxidation of propylene to carbon dioxide and the oxidation of carbon monoxide to carbon dioxide.

Exam A

Raw gases with a composition of 800 ppm propylene, 8% oxygen and the balance nitrogen were preheated to 120 °C and then passed over the catalyst at a gas space velocity of 50,000 h L Propylene was converted to 99%. The same gas mixture, preheated to 90 °C, was passed over the catalyst at a gas space velocity of 20,000 h L with a propylene conversion of 99%.

Exam B

Raw gases with a composition of 2.5% carbon monoxide, 8% oxygen and the rest nitrogen were preheated to 80 °C and fed to the catalyst at a gas phase space velocity of 20,000 h L. The conversion value achieved in this case was 59% carbon monoxide.

The same gas mixture preheated to the same temperature was fed to the catalyst at a gas phase space velocity of 50,000 h ^-2 , with the achieved carbon monoxide conversion value being 99 The above temperature, i.e. 80 °C to 120 °C, must in fact be considered exceptional, since the best commercially available catalysts used in catalytic converters achieve the same conversions of polypropylene and carbon dioxide at the same space velocities as stated above, but at a temperature that never falls below 150 °C.

Example 16

This example will illustrate the activity of the inventive aluminum-modified silica catalyst, designated TRS-57, prepared according to the procedure of Example 6, in the alkylation of benzene with ethylene.

The reaction was carried out in a tubular reactor with a fixed bed of 8 mm internal diameter and electrically heated. 1.2 milliliters (0.85 grams) of catalyst with a particle size ranging from 600 to 300 μm was placed in the reactor. Benzene was then fed by a metering pump, first to a preheating system, where it was combined with a pre-selected amount of ethylene, and then to the reactor. The stream leaving the reactor was analyzed by gas chromatograph. The results obtained are shown in Table 7 below.

Table No. 7

Alkylation of benzene with ethylene catalyst: TRS-57, pressure: 2 MPa, temperature: 440 °C, liquid phase space velocity: 14 h ^-1 , molar ratio = 7

Operating time (h) Amount of ethylbenzene in the product (% molar) Amount of diethylbenzene in the product (% molar) Ethylene conversion (%)

10 13.9 1.35 100.0 ⁵⁰ 13.9 1.35 100.0 100 14.0 1.3Q 100.0 150 13.8 1.30 98.8 200 13.9 1.35 100.0 250 13.7 1.28 97.9 300 12.5 1.02 87.6 350 11.3 0.90 78.9

Example 17

According to this example, the catalyst used in Example 16 for alkylation with ethylene, designated TRS-57, was subjected to regeneration which was carried out in situ with a stream of air diluted with nitrogen at a temperature of 500°C.

After the regeneration, the catalyst was reused for the alkylation of benzene with ethylene. The results are shown in Table 8, and it is evident from these results that it is very advantageous to regenerate the catalyst.

Table No. 8

Alkylation of benzene with ethylene

Catalyst: regenerated TRS-57, pressure: 2 MPa, temperature: 440 °C, liquid phase space velocity: 14 h ¹ , molar ratio CgH ₆ :C ₂ H ₄ = 7.

Operating time (h) Amount of ethylbenzene in the product (% molar) Amount of diethylbenzene in the product (% molar) Ethylene conversion (%) 10 14.0 1.30 100.0 50 13.9 1.35 100.0 100 13.8 1.40 100.0 150 13.8 1.35 100.0 200 13.8 1.40 100.0 ‘ 250 13.2 1.19 93.8 300 12.8 0.95 88.5

Example 18

This example illustrates the activity of the inventive aluminum-modified silica catalyst, designated TRS-57, prepared according to the procedure of Example 6, in the alkylation of benzene with ethanol.

The reaction was carried out by loading 1.2 milliliters (0.85 grams) of catalyst with a particle size ranging from. into an electrically heated tubular fixed bed reactor.

600 to 300 µm. The reaction mixture containing benzene and ethanol was then fed by a dosing pump, first into the preheating system and then into the reactor. The outlet stream was analyzed by gas chromatography. The results obtained are shown in Table 9.

Table No. 9

Alkylation of benzene with ethanol

Catalyst: TRS-57, pressure: 2 MPa, temperature: 440 °C, liquid phase space velocity: 10 h ^_1 , molar ratio CgH ₆ :C ₂ H ₅ OH = 5

Operating time (h) Amount of ethylbenzene in the product (% molar) Amount of diethylbenzene in the product (% molar) Conversion of _C2HjOH (%) 50 18.8 1.3 100 100 19.0 1.2 100 150 18.8 1.3 100 200 19.0 1.2 100 250 19.0 1.2 100 300 19.0 1.2 100 400 19.0 1.2 100

A specific feature of the modified silicas obtained by the process according to the invention is their potential use as catalysts for the alkylation of hydrocarbons, olefins and/or paraffins to high octane hydrocarbons. As mentioned above, these alumina-modified silicas are porous, have a specific surface area greater than 150 m2/g and have a composition according to the general formula given above.

The following example will illustrate this specific application possibility of modified silicas prepared by the process according to the invention.

Example 19

In this embodiment, porous crystalline silica prepared according to the procedure of Example 5, into the crystal lattice of which aluminum was introduced as a substitute for silicon, was used as a catalyst for the alkylation of isobutane with normal butenes.

Into the small reactor described in Example 7, 3 milliliters of catalyst (1.9 grams) with a particle size ranging from 600 to 300 µm was charged.

The conditions used in this procedure and the results obtained are shown in the following table 10.

Table 10 * Pressure: 2 MPa, molar ratio of isobutene to n-butene: 15 Temperature Space velocity (h Alkylation based on butenes (%) Product composition 250 1.3 100 about 90% isoparaffins 20% aromatics and about 350 1.3 100 about 50% isoparaffins 50% aromatics and about 350 5.0 90 about 70% isoparaffins 30% aromatics and about

SUBJECT OF THE INVENTION

Claims (8)

OBJECT OF THE INVENTION A process for producing aluminum modified silica having a porous crystalline structure having a specific surface area greater than 150 m / g of the general formula: Si. (0.001 2 to 0.005 0) Al. O _y in which y is a number in the range of 2,001 8 to 2,007 5, and with a molar ratio of SiCl 2 / Al 2 O 6 in the range of 38 to 816, characterized in that the compound is reacted in an aqueous, alcoholic or aqueous-alcoholic solution silicon selected from the group consisting of silica and tetraalkyl orthosilicates, with an aluminum compound such as aluminum nitrate or aluminum acetate in the presence of a clathrate reagent selected from the group consisting of tertiary amines, aminoalcohols, tetraalkylammonium hydroxides having 1 to 5 carbon atoms in the alkyl moiety, and triethanolamine wherein optionally one or more mineralizing agents and optionally an inorganic basic compound are added, the mixture is left to crystallize in a closed medium for 5 to 20 days at a temperature of 100 to 220 ° C, after which it is allowed to cool and after air filtration and drying at a temperature ranging from 300 to 700 ° C for a period of time 2 to 24 hours, optionally washed with boiling distilled water containing the ammonium salt and calcined again under the above conditions. 2. The process of claim 1 wherein said tetraalkyl ortho-silicate is tetraethyl ortho-silicate or tetramethyl ortho-silicate. 3. The process of claim 1, wherein said mineralizing agent is an alkali or alkaline earth metal halide or hydroxide. 4. The process of claim 3 wherein the alkali and alkaline earth metal hydroxides and halides are selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, potassium bromide, sodium bromide, sodium iodide, calcium iodide, or sodium hydroxide. calcium bromide. Process according to claim 1, characterized in that alkali and / or alkaline earth metal hydroxides and / or ammonia hydroxides are used as inorganic bases. 6. The process of claim 5, wherein the alkali and alkaline earth metal hydroxides are selected from the group consisting of sodium hydroxide, potassium hydroxide, and calcium hydroxide. 7. The method of claim 1, wherein the amount of inorganic base and / or tetraalkylammonium hydroxide or triethanolamine is less than a stoichiometric amount relative to the silica. The process according to claim 7, characterized in that the amount of inorganic base and / or tetraalkylammonium hydroxide or triethanolamine is 0.05 to 0.50 mol per mol of silica.