WO2004039726A1

WO2004039726A1 - Mesoporous structures having high catalytic activity in acid catalysis reactions and preparation method thereof

Info

Publication number: WO2004039726A1
Application number: PCT/ES2003/000544
Authority: WO
Inventors: Javier AGÚNDEZ RODRÍGUEZ; Isabel DÍAZ CARRETERO; Carlos MÁRQUEZ ÁLVAREZ; Joaquín PÉREZ PARIENTE; Enrique SASTRE DE ANDRÉS
Original assignee: Consejo Superior De Investigaciones Científicas
Priority date: 2002-10-31
Filing date: 2003-10-24
Publication date: 2004-05-13
Also published as: ES2206064A1; AU2003274160A1; ES2206064B1

Abstract

The invention relates to novel mesoporous aluminosilicate-type materials having a chemical composition with the following formula (in oxide moles): Al2O3: m SiO2: n M2O, wherein: m denotes a value of between 10 and 1000, preferably between 20 and 200; M denotes cations Na+ or H+; and n denotes a value of between 0.001 and 1, preferably between 0.01 and 1. The inventive materials comprise regularly-distributed pores having an average diameter of between 2 and 10 nm. Moreover, said materials also present a high catalytic activity in acid catalysis reactions. The invention also relates to the method of preparing said materials and to the use thereof as catalysts for hydrocarbon transformation reactions, such as cracking, isomerisation, transalkylation, alkylation, dimerisation and polymerisation.

Description

TITLE

MESOPOROUS STRUCTURES WITH HIGH ACTIVITY

CATALYTICS IN REACTIONS OF ACID CATALYSIS AND ITS

PREPARATION PROCEDURE

SECTOR OF THE TECHNIQUE

This invention relates to mesoporous aluminosilicate materials that possess a high catalytic activity in acid catalysis reactions, their preparation process and their use as a catalyst for hydrocarbon transformation reactions, such as cracking, isomerization, transalkylation, alkylation, dimerization and polymerization.

STATE OF THE TECHNIQUE

Zeolitic materials are widely used as catalysts in the refining and petrochemical industries and in the synthesis of chemical compounds of high added value. Its catalytic behavior is due to the presence in these materials of active centers of high acidity, which allow catalyzing a large number of reactions of industrial interest.

Both zeolites (crystalline aluminosilicates) and zeolitic materials in general have a crystalline structure in which there are cavities and channels

_* microporous, whose access is limited by openings whose diameter is always less than 2.0 nm, and in most cases does not exceed 0.8 nm. Although the size of the cavities and channels present in the structure of the zeolites and zeolitic materials is suitable for transforming or producing molecules that are small enough, for example to produce an isomer excluding other possible ones (property known as shape selectivity), it is a often too small to transform bulky molecules, which cannot access the interior of the microporous system. This implies a severe limitation for the use of zeolites and zeolitic materials in numerous chemical processes of industrial interest. In 1992, the Mobil Oil company announced the invention of a new family of ordered mesoporous materials, called M41S (WO Pat. 91/11390 (1991)). These materials are characterized by having a regular distribution of pores whose size, between 2.0 nm and 10.0 nm, is within the range of the mesopore, so they do not have the limitations of zeolites to process bulky molecules. However, despite having a regular distribution of mesopores, these materials are amorphous, that is, the inorganic skeleton is constituted by a network of tetrahedra of SiO ₄ and AlO ₄ linked together in a disorderly manner through oxygen atoms . For this reason, the acidity of these materials resembles that of amorphous silica-aluminas, being much lower than that of zeolites, as well as their catalytic activity. These factors severely limit the use of mesoporous materials ordered in numerous processes of industrial interest.

Recently, a method for obtaining mesoporous materials from precursor solutions of crystals of the Y-type zeolite faujasite containing the tetramethylammonium cation and having a high catalytic activity in acid catalysis reactions has been described. (Pat. ES 200201821)

DESCRIPTION OF THE INVENTION Brief Description

This invention relates to new mesoporous materials with a chemical composition expressed by the following formula (in moles of oxides):

At ₂ O ₃ : m SiO ₂ : n M ₂ O

wherein the value of m is between 10 and 1000, preferably between

20 and 200; M represents the Na ⁺ or Ε cations, and the value of n is between 0.001 and 1, preferably between 0.01 and 1.

These materials have a regular distribution of pores whose average diameter is between 2.0 nm and 10 nm. They also have a high catalytic activity in acid catalysis reactions. Its preparation process is described from precursor solutions of colloidal size ZSM-5 zeolite crystals and its use as catalysts for hydrocarbon transformation reactions, such as cracking, isomerization, transalkylation, alkylation, dimerization and polymerization. Description of the invention

The present invention relates to the preparation of porous structures that have a lattice formed by the union of tetrahedra of SiO ₄ and AlO ₄ , with a molar ratio of silicon to aluminum between 5 and 500, which have a regular distribution of pores whose average diameter is between 2.0 nm and 10 nm, at least one X-ray diffraction peak corresponding to a spacing between 1.5 nm and 20.0 nm, a BET surface between 300 m ² / g and 1400 m ² / g, a total pore volume comprised between 0.2 cm ³ / g and 2.0 cm ³ / g, a catalytic activity in m-xylene transformation such that for a contact time value expressed as WF (gh / mol) between 0.5 and 1 the conversion of m-xylene at 400 ° C is at least 5%, and its use as catalysts for transformation reactions of organic molecules that are catalyzed by acid centers.

The process for obtaining the porous materials object of the present invention comprises a two step process. In the first stage, a solution A, called "colloidal ZSM-5 zeolite precursor solution" is prepared, whose main but not only feature is that it contains the tetrapropylammonium cation. In a second stage, a solution B is prepared whose main but not the only characteristic is that it contains a cationic surfactant, which is mixed with solution A. It is characteristic of the present invention that solution A containing the tetrapropylammonium cation is a crystal precursor Colloidal size of the zeolite ZSM-5. It is well known that the preparation of colloidal-sized zeolite crystals requires synthesis conditions that are different from those used to obtain non-colloidal zeolite crystals (Persson, AE, Schoeman, BJ, Sterte, J., Otterstedt, JE , Zeolites, 14 (1994) 557-567; Zeolites, 15 (1995) 611-619). This is a specific feature of the present invention that the difference from other methods that make use of ZSM-5 seeds that do not give rise to colloidal crystals of ZSM-5 (WO 01/92154 Al, Pinnavaia, TJ, Zhang, W. ₅ and Liu, Y.).

The chemical composition of solution A is represented by the formula (in moles):

Al ₂ O ₃ : x SiO ₂ : y (TPA) ₂ O: z Na ₂ O: w H ₂ O: v ROH The preparation of this solution comprises the treatment of an aluminum source, such as aluminum hydroxide, with an aqueous solution of tetrapropylammonium hydroxide and optionally also with a sodium source, until the dissolution of the aluminum hydroxide is achieved. Non-limiting examples of that source of sodium are sodium hydroxide and various soluble sodium salts, such as sodium chloride, sodium sulfate or sodium nitrate. The aluminum hydroxide used in the invention can be advantageously prepared by precipitation from a solution of a soluble aluminum salt, such as aluminum sulfate or aluminum nitrate, by mixing it with a solution of a base, such as ammonium hydroxide. Optionally, metallic aluminum can be dissolved in the tetrapropylammonium hydroxide solution.

In the case where aluminum hydroxide is used as an aluminum source, the treatment of said hydroxide with the basic solution containing tetrapropylammonium and optionally a sodium source is carried out at a temperature between 10 ° C and 100 ° C, preferably between 20 ° C and 60 ° C, for a time between 5 minutes and 5 hours, preferably between 10 minutes and 1 hour. The objective of this treatment is to achieve the complete dissolution of aluminum hydroxide.

Once the source of aluminum is dissolved in the tetrapropylammonium hydroxide solution, the resulting solution is mixed with a source of silicon, non-limiting examples of which are colloidal silica, precipitated silica, pyrogenic silica, or silicon alkoxides, such as tetramethoxysilane and tetraethoxysilane. Optionally, the silicon source can be reacted with a part of the tetrapropylammonium hydroxide solution used in the preparation. If colloidal silica is used as a source of silicon, it can optionally be treated with a cation exchange resin in order to reduce the content of alkali cations, preferably sodium, which it contains. The value of x in the composition of solution A is between 25 and 1000, preferably between 50 and 200.

Optionally, solution A may contain one or more alcohols (ROH) having a number of carbon atoms between 1 and 6, may be linear or branched, and preferably methanol, ethanol or mixtures of both. The values of y, z, w and v in the composition of solution A are such that the molar ratios y / x, z / x, w / xyv / x are within the following ranges: y / x between 0.05 and 1, preferably between 0.1 and 0.5. z / x between 0 and 1, preferably between 0.01 and 0.1. w / x between 5 and 100, preferably between 10 and 50. v / x between 0 and 50, preferably between 0.1 and 10.

Once solution A is prepared, it is aged at a temperature between 4 ° C and 150 ° C, preferably between 20 ° C and 110 ° C, for a time between 10 minutes and 7 days, preferably between 1 hour and 48 hours. It is characteristic of the present invention that the aging of solution A is carried out under conditions of temperature and time such that the formation of ZSM-5 crystals is not detected at the end of aging. For this reason, solution A is referred to herein as the "ZSM-5 colloidal zeolite precursor solution".

Solution B is prepared by dissolving one or more cationic surfactants in water, in an organic solvent or in a mixture of both. The cationic surfactant used in the present invention is represented by the formula NRiR ^ Rt, wherein R ₂ , R ₃ and P may be the same or different, and represent organic groups containing between 1 and 6 carbon atoms, the preferred composition being one in which R ₂ = R ₃ = P ^ = CH ₃ ; Rt represents an organic group containing carbon and hydrogen, saturated or unsaturated, preferably a linear or branched aliphatic chain, containing a number of carbon atoms between 2 and 36, preferably between 8 and 22. Non-restrictive examples of this cationic surfactant they are hexadecyltrimethylammonium, dimethyldidodecylammonium and benzyltrimethylammonium. This cation can be used in the form of salts, non-limiting examples of which are bromide and chloride, or as hydroxide, or mixture of both. The solution B referred to in the invention may contain one or more of the surfactants described, and their proportion by weight with respect to the solvent is between 2 and 50%, preferably between 10% and 30%. The preferred solvent for preparing solution B is water, but optionally an alcohol or mixture of two or more alcohols, or a mixture of alcohols with water. The alcohols used may contain a number of carbon atoms between 1 and 6, preferably methanol or ethanol. Optionally, solution B may contain tetramethylammonium and optionally also sodium, in a proportion not exceeding 90% of tetramethylammonium and 90% of sodium contained jointly in solutions A and B.

The molar ratio between the silicon of solution A, expressed as SiO ₂ , and the cationic surfactant of solution B (silica / surfactant ratio) is between 0.1 and 15, preferably between 0.5 and 5. Solution B it may contain a proportion of the total solvent used in the preparation between 1% and

95%, preferably between 10% and 50%.

The gel resulting from the mixture of solutions A and B is treated at a temperature between 4 ° C and 200 ° C, preferably between 20 ° C and 180 ° C, for a time between 30 minutes and 7 days, preferably between 1 hour and 48 hours. The solid product obtained after this heating step is filtered, washed with deionized water and dried.

The product thus obtained is heated in air at temperatures between

400 ° C and 800 ° C, preferably between 500 ° C and 700 ° C, in order to remove the organic matter it contains. Optionally, the heat treatment can be carried out in an atmosphere of an inert gas, such as nitrogen, optionally followed by an air calcination.

The calcined material obtained by the process described in the present invention is characterized by having a chemical composition expressed by the following formula (in moles of oxides):

At ₂ O ₃ : m SiO ₂ : n M ₂ O

wherein the value of m is between 10 and 1000, preferably between 20 and 200; M represents the Na ⁺ or H ^"1" cations, and the value of n is between 0.001 and 1, preferably between 0.01 and 0.9. In addition to its chemical composition, the porous material obtained according to the process described in the present invention is distinguished by having the following characteristics:

1) At least one X-ray diffraction peak corresponding to a spacing value between 1.5 nm and 20 nm.

2) A total pore volume (N) between 0.2 cm ³ / g and 2.0 cm ³ / g.

3) A BET surface (A) between 300 m ² / g and 1,400 m ² / g.

4) An average pore diameter (expressed as 4N / A) between 2.0 nm and 10 nm. 5) A characteristic inherent to the material claimed in the present invention is its high catalytic activity in reactions that are catalyzed by acid solids. In the present invention that catalytic activity is expressed by way of non-limiting example in the degree of conversion of m-xylene when a certain amount of this reagent is flowed into a tubular reactor through a bed containing a certain amount of the material heated to a certain temperature. More specifically, the fact that in a fixed bed tubular reactor using nitrogen as a carrier gas (molar ratio Ν ₂ / m-xylene = 4), at a contact time W / F (W / F, is a characteristic of the material It is expressed in grams of catalyst per hour and per mole of m-xylene) between 0.5 and 1 and at a temperature of 400 ° C, allows to obtain a conversion of m-xylene equal to or greater than 5%.

It is characteristic of the material obtained according to the process described in the present invention to simultaneously possess all the characteristics indicated above, which distinguishes it from other materials described above in the literature that may possess one or more, but not all, the characteristics of the claimed material. in the present invention.

The material described in the invention can be used in a wide variety of hydrocarbon transformation reactions, among which are examples of catalytic cracking, isomerization, hydroisomerization, hydrocracking, alkylation, dimerization and polymerization, and among them, non-limiting example the conversion of m-xylene. DESCRIPTION OF THE FIGURES

Figure 1. X-ray diffractogram (CuKα radiation) of the calcined sample obtained according to the procedure described in example 1. The diffractogram in the region of values of 2Θ between 4 ° is included in the box that appears inside the figure. and 40 °.

Figure 2. Nitrogen adsorption-desorption isotherm (-196 ° C) of the calcined sample obtained according to the procedure described in Example 1

EXAMPLES OF REALIZATION

The following examples illustrate the invention, without thereby constituting a limitation of the invention. Example 1

A solution A is prepared with the following composition:

At ₂ O ₃ : 100 SiO ₂ : 12 (TPA) ₂ O: 0.40 Na ₂ O: 2120 H ₂ O: 400 ETOH

For this, a solution of 3.78 g of aluminum sulfate in 40 g of milliQ water is prepared. The Al (OH) ₃ is precipitated by adding 4.4 g of NH ₄ OH (30% by weight aqueous solution), filtered and washed with deionized water.

32.83 g of TPAOH (42.2% aqueous solution by weight), 84.92 g of milliQ water and 0.09 g of NaOH are introduced into a polypropylene (PP) canister. Stir for 15 minutes and then add Al (OH) ₃ . It is stirred until the aluminum hydroxide is completely dissolved, which occurs in 20 minutes. Then 59.02 g of tetraethylorthosilicate are added. The resulting gel is stirred an additional 30 minutes, and aged at a temperature of 80 ° C for 5 hours.

After this time, allow to cool to room temperature and add

17.55 g of an aqueous solution of cetyltrimethylammonium bromide (CTAB) (20% by weight), called solution B. The resulting mixture is maintained at a temperature of 25 ° C for 3 hours. After this time, the resulting suspension is filtered, and the solid is washed and dried. The dried solid product is calcined at a temperature of 550 ° C in a flow of N ₂ for 1 h, followed by air at the same temperature for 6 h.

The X-ray diffraction diagram of the calcined solid is presented in Figure 1, in which the presence of an intense peak corresponding to a spacing value d = 3.9 nm can be observed. The BET surface of the sample is 1,073 m ² / g, its pore volume is 1.08 cm ³ / g and its average pore diameter is 4.0 nm. The chemical composition of the solid (by weight) is: 98% SiO, 1.9% Al O ₃ and 0.04% Na O. Figure 2 shows the nitrogen adsorption isotherm of the calcined solid, in which the characteristic stage of filling the mesopores around a partial pressure p / p ₀ of 0.35 is observed. In the m-xylene transformation reaction, at 400 ° C, for a nitrogen / m-xylene molar ratio of 4 and at a contact time (expressed as W / F (mol g / h)) of 0.70 this sample produces a reagent conversion of 15%.

Example 2

A solution A is prepared with the following composition:

For this, a solution of 7.56 g of aluminum sulfate in 80 g of milliQ water is prepared. The Al (OH) ₃ is precipitated by adding 8.8 g of NIL ₄ OH (30%) to the solution, filtered and washed with deionized water.

65.66 g of TPAOH (42.2% aqueous solution by weight), 169.84 g of milliQ water and 0.18 g of NaOH are introduced into a polypropylene (PP) canister. Stir for 15 minutes and then add Al (OH) ₃ . It is stirred until the aluminum hydroxide is completely dissolved, which occurs in 20 minutes. Then 118.04 g of

Tetraethylorthosilicate. The resulting gel is stirred an additional 30 minutes, and aged at a temperature of 80 ° C for 5 hours.

After this time, it is allowed to cool to room temperature and 35.1 g of an aqueous solution of cetyltrimethylammonium bromide (CTAB) (20% by weight), called solution B, is added. The resulting mixture is heated to a temperature of 80 ° C for 3 hours. After this time, the resulting suspension is filtered, and the solid is washed and dried.

The dried solid is calcined at 550 ° C in N ₂ flow for 1 h, followed by air at the same temperature for 6 h. The X-ray diffraction diagram of the calcined solid has an intense peak at a spacing value of 3.5 nm; a BET area of 896 m ² / g; a pore volume of 0.93 cm ³ / g and an average pore diameter of 4.2 nm. The chemical composition of the solid by weight is 98% SiO ₂ , 1.9% Al ₂ O ₃ and 0.03% Na ₂ O. In the m-xylene transformation reaction, at 400 ° C, for a nitrogen / hydrocarbon molar ratio of 4 and at a contact time (expressed as W / F (mol g / h)) of 0.62, this sample produces a reagent conversion of 8%.

Claims

1) A mesoporous aluminosilicate type material that has a high activity in transformation reactions of organic molecules catalyzed by acid centers, and characterized in that it has the chemical composition expressed by the following formula (in moles of oxides):

At ₂ O ₃ : m SiO ₂ : n M ₂ O where the value of m is between 10 and 1000, preferably between 20 and 200; M represents the Na ⁺ or ϊÚ cations, and the value of n is between 0.001 and 1, preferably between 0.01 and 1, and which is further characterized by having the following properties: a) at least one ray diffraction peak X corresponding to a spacing value between 1.5 nm and 20 nm, b) a total pore volume between 0.2 cm / g and 2.0 cm / g, c) a BET surface area between 300 m / g 1,400 m / g, d) an average pore diameter between 2.0 nm and 10 nm, e) a catalytic activity in m-xylene transformation such that for a value of W / F (gh / mol) between 0.5 and 1 the conversion of m-xylene is at least 5%.

2) A process for obtaining the mesoporous aluminosilicate type material described in claim 1, characterized in that it is carried out by mixing a solution A called "colloidal zeolite ZSM-5 precursor solution", and a solution B, characterized in that it contains a cationic surfactant.

3) A process for obtaining the porous aluminosilicate type material described in claim 1 according to claim 2 characterized by the following steps: a) heating the gel resulting from the mixture of solutions A and B at a temperature between 4 ° C and 200 ° C, preferably between 20 ° C and

180 ° C, for a time between 30 minutes and 7 days, preferably between 1 hour and 48 hours, b) the solid product obtained in a) is filtered, washed with deionized water and dried, and c) the product thus obtained is heated in air at temperatures between 400 ° C and 800 ° C, in order to eliminate the organic matter it contains. Optionally, the heat treatment can be carried out in an atmosphere of an inert gas, such as nitrogen, which can optionally be continued with an air calcination.

4) A process for obtaining the porous aluminosilicate type material described in claim 1, characterized in that the preparation of solution A according to claims 2 and 3 consists of the following steps: a) treatment of an aluminum source, such as hydroxide of aluminum, or soluble salts of aluminum, such as aluminum sulfate or aluminum nitrate, or metallic aluminum, with an aqueous solution of tetrapropylammonium hydroxide which may optionally also contain a source of sodium, such as sodium hydroxide, chloride sodium or sodium sulfate, until a solution is obtained, b) mixing the solution of a) with a source of silicon, such as colloidal silica, precipitated silica, pyrogenic silica or silicon alkoxides such as tetramethoxysilane and tetraethoxysilane, and c) aging of the solution thus obtained at a temperature between 4 ° C and 150 ° C, preferably between 20 C and 110 ° C, for a time between 10 minutes and 7 days, preferably 1 hour to 48 hours.

5) A process for obtaining the mesoporous aluminosilicate type material described in claim 1 prepared as described in claims 2 to 4 characterized in that the chemical composition of solution A is represented by the formula (in moles):

Al ₂ O ₃ : x SiO ₂ : y (TPA) ₂ O: z Na ₂ O: w H ₂ O: v ROH

in which the value of x is between 20 and 1000 and the values of y, z, w and v are such that the molar ratios y / x, z / x, w / xyv / x fall within the following intervals: a ) and / x between 0.05 and 1, preferably between 0.1 and 0.5. b) z / x between 0 and 1, preferably between 0.01 and 0.1. c) w / x between 5 and 100, preferably between 10 and 50. d) v / x between 0 and 50, preferably between 0.1 and 10.

6) A process for obtaining the porous aluminosilicate type material described in claim 1 prepared as described in claims 2 to 5 characterized in that the solution A may contain one or more linear or branched alcohols, represented by the expression ROH in the formula of claim 5, containing a number of carbon atoms between 1 and 6. 7) A process for obtaining the porous aluminosilicate type material described in claim 1 prepared as described in claims 2 to 6 characterized in that the solution B is prepared by dissolving one or more cationic surfactants in water, in an organic solvent or in a mixture of both; in general, the cationic surfactants used are represented by the formula NRiR ^ i, where R ₂ , R and t may be the same or different, and represent organic groups containing between 1 and 6 carbon atoms, the preferred composition being that in the that R = R ₃ ^ i = CH ₃ ; R \ represents an organic group containing carbon and hydrogen, saturated or unsaturated, preferably a linear or branched aliphatic chain, containing a number of carbon atoms between 2 and 36.

8) A process for obtaining the porous aluminosilicate type material described in claim 1 prepared according to claim 7, characterized in that the cationic surfactant is selected, among others, from the following group: hexadecyltrimethylammonium, dimethyldidodecylammonium, benzyltrimethylammonium, salts of said cations, among others , bromide salts, chloride, or as hydroxide, or mixture of both.

9) A process for obtaining the porous aluminosilicate type material described in claim 1 according to claims 7 and 8, characterized in that the solution B may contain one or more of the surfactants described, and the proportion by weight of these relative to the solvent is comprised between 2% and 50%.

10) A process for obtaining the porous aluminosilicate type material described in claim 1 prepared according to claims 2 to 9 characterized because the molar ratio between silicon, expressed as SiO ₂ , and the cationic surfactant (silica / surfactant) is between 0.1 and 15.

11) A process for obtaining the porous aluminosilicate type material described in claim 1 prepared according to claims 2 to 10, characterized in that the solution B can contain a proportion of the total solvent used in the preparation between 1% and 95% .

12) A process for obtaining the porous aluminosilicate type material described in claim 1 prepared according to claims 2 to 11, characterized in that the solvent used to prepare solution B can be water, one or more alcohols or a mixture of water and alcohols; These alcohols can be linear or branched, and can contain a number of carbon atoms between 1 and 6.

13) A process for obtaining the porous aluminosilicate type material described in claim 1 prepared according to claims 2 to 12, characterized in that solution B may contain tetrapropylammonium and optionally also sodium, in a proportion not exceeding 90% of tetrapropylammonium and 90 % of sodium contained in total in solutions A and B.

14) Use of the porous aluminosilicate type material according to claim 1 obtained according to the process described in claims 2 to 13, as a catalyst for hydrocarbon transformation reactions, such as cracking, isomerization, transalkylation, alkylation, dimerization and polymerization.

15) Use of the porous aluminosilicate type material according to claim 1 obtained according to the process described in claims 2 to 13, as a catalyst in the xylenes transformation reaction.