EP3030521A2

EP3030521A2 - Zeolites with hierarchical porosity

Info

Publication number: EP3030521A2
Application number: EP14790175.5A
Authority: EP
Inventors: Serge Nicolas; Karine LOPEZ; Cécile LUTZ; Ludivine Bouvier
Original assignee: Carbonisation et Charbons Actifs CECA SA
Current assignee: Arkema France SA
Priority date: 2013-08-05
Filing date: 2014-08-04
Publication date: 2016-06-15
Also published as: US10106429B2; CN105050954A; EA201592092A1; AU2014304409B2; JP2016522156A; CA2909798C; WO2015019013A2; FR3009300B1; KR101800526B1; CN105050954B; TWI544961B; ZA201508079B; CA2909798A1; SG11201508819WA; US20160137517A1; US20180362354A1; EA034181B1; BR112015027251A8; AU2014304409A1; BR112015027251A2

Abstract

The present invention concerns zeolites with hierarchical porosity having a molar ratio Si/AI of between 1 and 1.4, inclusive, of which the average diameter, as a number, is between 0.1 μm and 20 μm, having controlled and optimised crystallinity, and having mesoporosity such that the mesoporous outer surface area is between 40 m². g-1 and 400 m2.g-1. The present invention also concerns the method for preparing said zeolites with hierarchical porosity.

Description

ZEOLITES WITH HIERARCHISED POROSITY

The present invention relates to the field of zeolites, especially zeolites with hierarchical porosity, and in particular zeolites with hierarchical porosity of low Si / Al molar ratio, and especially zeolites with hierarchical porosity of low Si / Al molar ratio. of structure FAU and LTA.

Synthetic zeolites (that is to say non-natural) are of ever increasing interest in the industry, as evidenced by the many recent research work related to obtaining zeolites always more efficient, with synthetic processes always simpler, economic and easy to implement.

In recent years, hierarchical porosity zeolites (ZPH) are the subject of many scientific publications and patent applications. Thus, as early as 2005, the process for synthesizing zeolites with hierarchical porosity with good crystallinity (pure phase, observed by XRD) was described in application WO2007 / 043731, using an organosilane structuring agent.

The product obtained after calcination comprises a zeolite network connected to a network of mesopores of a few nanometers in diameter. The hydrothermal resistance of this product is much better than that of mesoporous solids type MCM-41 which allows to consider applications in which involves a thermal regeneration.

[0005] Other methods for the preparation of zeolite with hierarchical porosity, that is to say solids comprising a microporous network of zeolite type connected to a network of mesopores, have been developed and can be classified in the following way ( reviewed by DP Serrano, C em Soc Rev., (2013), 42, 4004-4035):

• Zeolitic structure postprocessing which consists of removing atoms from the zeolite network to create mesopores; this can be done either by acid treatments which dealuminate the solid followed by a washing with sodium hydroxide which eliminates the aluminic residues formed (J. Pérez-Ramirez et al., Adv Funct Mater., (2012), 1 - 12 or by treatments that combine the action of an acid with that of a structuring agent that promotes the formation of mesopores (see WO 2013/106816).

"Hard templating method" or "molding method" which consists of using a porous network (organic or inorganic) as a mold, this porous network is brought into contact with a reaction medium that can form a zeolite network by hydrothermal transformation, the crystallization of the zeolite is carried out then eliminates the mold either by calcination or by dissolution to generate mesoporosity (CJH Jacobsen, J. Am. C em. Soc., (2000), 122, 71 16-71 17).

Zeolitization of amorphous mesoporous solid such as mesoporous silicas formed according to the sol-gel technique described by M. Matsukata et al., (Top Catal., (1999), 9, 77-92).

• Direct synthesis mentioned at the beginning using an organosilane structuring agent, this type of structurant having the particularity of having on the one hand, an affinity with the silico-aluminas species which form the zeolite network thanks to its silane function and on the other hand, to be able to occupy a space with its long-chain organic function that occupies space and creates mesoporosity when it is eliminated (application WO2007 / 043731).

However, even if the solids obtained according to this direct synthesis method do indeed have a hierarchical porosity as shown by the nitrogen adsorption isotherms and the transmission microscopy photos (A. Inayat et al., Angew. Chem. Int.Ed., (2012), 51, 1962-1965), we find that:

The microporous volume of these hierarchically porous zeolites is significantly lower than that of non-mesoporous zeolites,

The structuring agent modifies the growth rates of the faces of the crystals, which makes it difficult to control the size of the crystals,

The increase in the structurant content to increase the mesoporous volume leads to a loss of selectivity for the crystallization of a given zeolite which results in the formation of an undesired zeolite structure mixture (Y. Meng et al. Asian Journal of Chemistry, 25 (8), (2013), 4423-4426).

One of the objectives of the present invention is to solve at least these three major drawbacks noted for direct synthesis using an organosilane type structuring agent.

Mention may also be made of the following documents, in which the use of structuring agents of the organosilane type and of organosilane derivatives is described, with the aim of synthesizing various zeolitic structures with hierarchical porosity including X and LTA zeolites. .

Thus R. Ryoo [Nature Materials, (2006), vol. 5, p. 718 et seq.) Describes the synthesis of LTA with mesoporosity and later (K. Cho et al., Chem.Mater., 21, (2009), 5664-5673) the synthesis of LTA-type mesoporous zeolites and their applications to them. catalysis. The diffractograms presented in Figure 2 of K. Cho's article (see above) show that there is no polluting crystalline phase. In contrast, the decrease in the intensity of the peaks, when there is addition of structuring agent and a fortiori when its quantity increases, proves a degradation of the crystalline framework (low microporosity).

The patent application EP2592049 proposes the synthesis of a zeolite having a very large and well organized mesoporosity, but with a marked degradation of the crystalline framework (very low microporosity). This method uses a specific structuring agent comprising three ammonium functions.

The work of W. Schwieger {Angew. Chem., Int. Ed., (2012), 51, 1962-1965) concern the synthesis of mesoporous zeolite type FAU (X) implementing a structuring agent. A single example shows the use of TPHAC ([3- (trimethoxysilyl) propyl] hexadecyldimethylammonium chloride as a structuring agent, with a TPHAC / Al ₂ O ₃ mole ratio of 0.06. The zeolite obtained in this example has a microporous volume of 0.26 cm ³ . g ^"1 and an outer surface of 130 m ^2. ^{g" 1.} The structurant content described (0.06) is in fact a maximum high limit. Indeed, a content greater than this value leads to the appearance of P type zeolite, even when the crystallization is carried out at low temperature. It does not seem possible to increase the mesoporous surface beyond 130 m ² . g ^"1 while maintaining a pure zeolite structure, without pollution by zeolite P.

The article by Y. Meng (Asian Journal of Chemistry, 25 (8), (2013), 4423-4426) discloses syntheses of mesoporous LTA zeolite using [3- (trimethoxysilyl) chloride). ) propyl] octadecyldimethylammonium (TPOAC), as a structuring agent, and presents a study of various synthesis parameters, including the amount of structuring agent used, the alkalinity of the reaction medium and the crystallization temperature.

It appears that an increase in the content of structuring agent which should lead to an increase in the mesoporous volume also has the effect of modifying the growth rates of the zeolite network, thus causing the appearance of other zeolitic crystalline phases and therefore formation of mixtures of zeolitic structures, which is not desired. In addition, the diffractograms in Figure 1 of this article show a lowering of crystallinity.

The aforementioned prior art also shows that the microporous volumes are significantly lower than the microporous volumes of equivalent non mesoporous zeolites (that is to say whose mesoporous outer surface as defined below is strictly less than 40. m ^2, g ^"1 ), which is very penalizing in applications where a high active site content is required.In addition, the size of the crystals is undergone and can not be modified. Finally, the preparation methods described in the prior art seem to be difficult to industrialize especially because of the high costs they can generate, and because of the synthesis times which are even longer than the desired increase the mesoporosity.

The main references of the post-treatments are discussed below. The document US2013 / 0183229 introduces an amount of Pluronic ^® of the same order of magnitude as the amount of zeolite X, carries out long liquid channel treatments followed by several calcination treatments while the document WO2013 / 106816 introduced treatment with a halide of cetyltrimethylammonium (CTA) coupled with an acid. The publication of J. Pérez-Ramirez et al. (ibid.), describes optimized post-treatments for zeolites X and LTA with, first treatment with H ₄ EDTA acid and then NaOH basic treatment and finally, a new acid treatment Na ₂ H ₂ EDTA.

Although these processes make it possible to prepare zeolites with hierarchical porosity as shown by the shape of the nitrogen adsorption isotherms of the solids obtained, it is important to note that these processes use amounts of complexing agent of the same order of magnitude. as the initial zeolite mass with multiple and long operations. In addition, the mass yield of these processes is less than 60% which further penalizes their productivity. These processes are therefore long, expensive and unproductive. In addition, the microporous volumes are greatly reduced by the different treatments.

The inventors have now discovered that the problems encountered in the prior art can be solved in whole or at least in part thanks to zeolites with hierarchical porosity according to the present invention.

In particular, an object of the present invention is to provide hierarchically porous zeolites combining a high microporous volume, optimal purities and adjustable crystal sizes. Another object of the present invention is to provide an economical, simple and easily industrializable process for the preparation of said zeolites.

Thus, and according to a first aspect, the present invention relates to a zeolite with hierarchical porosity having at least the following characteristics:

• molar ratio Si / Al of between 1 and 1, 4, limits included,

• average diameter in number of crystals between 0.1 μηη and 20 μηη, preferably between 0.1 μηη and Ι Ο μηι, more preferably between 0.5 μηη and 10 μηι, more preferably between 0.5 μηη and 5 μηη; μηη, terminals included,

• controlled and optimal crystallinity, and

Mesoporosity such that the mesoporous outer surface is between 40 m ² . g ^"1 and 400m ² .g ^-1 , preferably between 60 m ² .g ^-1 and 200 m ² .g ^-1 . According to a preferred embodiment, the zeolite according to the present invention is a zeolite of the FAU type, and in particular a zeolite X, MSX, LSX or an EMT type zeolite or an LTA zeolite, ie a zeolite A By zeolite MSX (Silica X medium) is meant a zeolite of the FAU type having an Si / Al atomic ratio of between about 1.05 and about 1.15 inclusive. By zeolite LSX (Low Silica X) is meant an FAU type zeolite having an Si / Al atomic ratio equal to about 1.

The characteristics mentioned above give the zeolite according to the present invention, improved properties and quite surprising and interesting, compared to only microporous zeolites or both microporous and mesoporous known from the prior art.

The size of the crystals of the zeolite according to the present invention is expressed by their number average diameter by scanning electron microscope (SEM) observation, as indicated below. The present invention also has the advantage of allowing to adjust and adjust this size of crystals, in particular according to the synthesis conditions explained below.

By zeolite of controlled and optimal crystallinity is meant on the one hand a zeolite comprising a pure zeolite phase, and more precisely consisting of a single zeolite phase or comprising, preferably consisting of up to 2% by weight , included terminal, of one or more other zeolitic or amorphous phases, called polluting phases (crystallinity determined by XRD, technique described hereinafter), and secondly a microporous volume νμρ corresponding to the equation νμρ = \ / _μρ κ ± 15%, preferably to equation νμρ = \ _μρ κ ± 10%, more preferably the equation νμρ = νμρ _κ ± 5%, where \ / _μρ κ represents the micropore volume measured under the same conditions for a zeolite of the same chemical nature and with the same crystalline structure, perfectly crystalline (according to ICDD base PDF-2, release 201 1) but not mesoporous within the meaning of the invention, ie whose external surface is strictly inferior at 40 m ² . g ^"1 .

For example, according to "Zeolite Molecular Sieves" by DW Breck, John Wiley and Sons, New York, (1973), Table 4.26, p 348, the microporous volume / μ _κ of a non-mesoporous LTA zeolite perfectly crystallized is equal to 0.30 cm ³ . g ^"1 , and in the same work and the same table 4.26, page 351, the microporous volume \ μρ _κ of a zeolite FAU NaX, Si / Al ratio between 1 and 1, 5, not mesoporous and perfectly crystallized is equal to 0.36 cm ³ .g ^-1 .

The calculation of the microporous volume is carried out by applying the methods known to those skilled in the art from the nitrogen or argon adsorption isotherm by applying, as indicated below, the Dubinin-Raduskevitch equation. . And, as a reminder, the calculation of the mesoporous outer surface is measured using the Harkins and Jura equation.

The hierarchically porous zeolites according to the invention are solids comprising a microporous network connected to a mesopore network, and thus make it possible to reconcile the properties of accessibility to the active sites of the mesoporous zeolites known from the prior art and those of maximum crystallinity and microporosity of so-called "classical" zeolites (without mesoporosity). Thus, the hierarchically porous zeolites of the present invention have unexpected properties and open new perspectives as to their fields of industrial applications.

In addition, the zeolites of the present invention may be subjected to one or more cationic exchanges (for example with alkali metal or alkaline earth metal salts), as is well known to those skilled in the art and commonly performed on conventional zeolites.

In another aspect, the present invention relates to the method for preparing zeolites with hierarchical porosity as just described. The method of the invention has the advantages of being easy to implement, easily transferable on an industrial scale, and this in particular because of the high yields of synthetic materials, the robustness of the process and its speed.

More specifically, the method for preparing the zeolite with hierarchical porosity according to the invention comprises at least the following steps:

a) preparing a so-called growth gel, by mixing a source of silica with a source of alumina, at a temperature of between 0 ° C. and 60 ° C.,

b) adding to the growth gel of step a) a nucleating agent, at a temperature between 0 ° C and 60 ° C,

c) adding to the reaction medium at least one structuring agent,

d) crystallization reaction by increasing the temperature,

e) filtration and washing of the zeolite crystals obtained, and

f) drying and calcination.

It should be understood that step c) of adding agent (s) structurant (s) can be operated simultaneously with the steps a) and / or b) or before and / or after the steps a) and / or b). In all cases, the structuring agent must be present in the reaction medium before step d) of crystallization. However, it is preferred to add the structuring agent after step b). In addition, a latency time (rest time, with or without agitation) can be provided between steps a), b), c) and d). In a preferred aspect, the growth gel comprises a homogeneous mixture of a source of silica (for example sodium silicate), a source of alumina (for example alumina trihydrate), a strong mineral base, such as for example, sodium hydroxide, potassium hydroxide, or calcium hydroxide to name only the main and most commonly used, and water.

The process of the present invention is characterized by the use of the seeding technique with at least one nucleating agent well known to those skilled in the art, for example chosen from a nucleating gel, a crystal, for example for example, a zeolite crystal, a mineral particle of any kind, for example kaolin, meia-kaolin, or other clay, and the like, and mixtures thereof.

Without wishing to be bound by the theory, it is believed that the nucleating agent promotes the orientation of the synthesis towards the desired zeolite. In addition, and thanks to the presence of the nucleating agent, it is possible to use a larger amount of structuring agent than that described in the prior art without disturbing or slowing the crystallization of the zeolite network.

In a preferred aspect, the nucleating agent is a nucleation gel, and more preferably, said nucleating gel comprises a homogeneous mixture of a source of silica (for example sodium silicate), a source of alumina (for example alumina trihydrate), a strong mineral base, such as, for example, sodium hydroxide, potassium hydroxide, or calcium hydroxide to name only the main and most commonly used, and water.

The homogeneity of the mixture can be obtained by any method well known to those skilled in the art, and for example and without limitation by means of a paddle stirrer, a mixer, or to using an Archimedean screw type mixer as described in patent EP0818418.

By way of non-limiting example, in a 3 liter reactor, with an Archimedean screw whose rotation is set at 300 rpm ^"1 , a satisfactory homogeneity is obtained between a few minutes and a few tens of minutes. usually between 20 minutes and 30 minutes.

The mixture is generally prepared at temperatures between 0 ° C and 60 ° C, preferably between 10 ° C and 40 ° C, and for practical and economic reasons, the mixture is prepared more preferably at temperature. ambient, for example at 25 ° C. The homogenization period is then generally less than 2 hours.

The method of the present invention is further characterized by the addition to the growth gel thus obtained of a nucleating agent, and preferably a gel of nucleation according to the concept defined in US3947482. The added amount of nucleating agent can vary in large proportions, and the amount of nucleation gel added can generally be from 0.1% to 20%, preferably from 0.5% to 15% by weight, of more preferably between 1% and 10% by weight, inclusive, based on the weight of the growth gel.

When the nucleating agent is a zeolite crystal, it is preferably a zeolite crystal of the same nature as the zeolite that is desired to synthesize. The size of the crystal can vary in large proportions, and for example is typically between 0.1 μηη and 10 μηη. According to a preferred embodiment, the zeolite crystal is introduced in the form of an aqueous suspension. The quantity of crystals introduced can also vary in large proportions and is generally between 0.1% and 10% by weight relative to the total weight of growth gel.

As indicated above, the method of the present invention is a method of direct synthesis of zeolite with hierarchical porosity, and not a method where the hierarchized porosity results from a post-treatment of an already synthesized zeolite. However, it would not be outside the scope of the invention, by operating a subsequent post-processing step of the zeolite as synthesized.

Thus, the method of the present invention comprises an addition step in the mixture [growth gel / nucleating agent] obtained in step b) of at least one structuring agent.

The structuring agents that can be used are of all types known to those skilled in the art and in particular those described in the application WO2007 / 043731. According to a preferred embodiment, the structuring agent is advantageously chosen from organosilanes and more preferably from [3- (trimethoxysilyl) propyl] octadecyldimethylammonium chloride, [3- (trimethoxysilyl) propyl] hexadecyldimethylammonium chloride, [3- (trimethoxysilyl) propyl] dodecyldimethylammonium chloride, [3- (trimethoxysilyl) propyl] octylammonium chloride, N- [3- (trimethoxysilyl) propyl] aniline, 3- [2- (2-aminoethylamino)] ethylamino] propyltrimethoxysilane, N- [3- (trimethoxysilyl) propyl] -N '- (4-vinylbenzyl) ethylenediamine, triethoxy-3- (2-imidazolin-1-yl) propylsilane, 1 - [3- (trimethoxysilyl) propyl] urea, N- [3- (trimethoxysilyl) propyl] ethylenediamine, [3- (diethylamino) propyl] trimethoxysilane, (3-glycidyloxypropyl) trimethoxysilane, 3- (trimethoxysilyl) propyl methacrylate , [2- (cyclohexenyl) ethyl] triethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, (3-a minopropyl) trimethoxysilane, (3-mercaptopropyl) trimethoxysilane, (3-chloropropyl) trimethoxysilane, as well as mixtures of two or more of them in all proportions. Among the structuring agents listed above, [3- (trimethoxysilyl) propyl] octadecyldimethylammonium chloride, or TPOAC, is particularly preferred.

It is also possible to use structuring agents of higher molar mass and for example PPDA (Polymer Poly-Diallyldimethylammonium), PVB (PolyVinyl Butyral) and other oligomeric compounds known in the art for increasing the diameter of the mesopores.

The amount of agent (s) structurant (s) can vary in large proportions and in general it is such that the molar ratio of agent (s) structuring (s) / AI ₂ 0 ₃ starting is included between 0.005 and 0.20, preferably between 0.01 and 0.15, more preferably between 0.02 and 0.08 inclusive.

The addition of the structuring agent (s) is carried out with stirring, for example as indicated previously in step a), and then the mixture is subjected to a maturation step, preferably with stirring, always at the same temperature, for example at 25 ° C, for a time varying from a few minutes to several tens of minutes, typically for one hour, with stirring at 300 rpm ^"1 .

[0048] After this aging step, the reaction mixture is initiated in step d) crystallization, still under agitation, but slower, typically between 20 tr.min ^"1 and 100 ^{r" 1,} e.g. 50 rpm ^"-1 , and increasing the temperature to a value between 60 ° C and 100 ° C, for example 75 ° C. The time required for crystallization is generally between a few hours and several tens of hours. hours, advantageously between 8 hours and 48 hours.

At the end of the crystallization step, the zeolite crystals are extracted from the reaction medium by filtration, then washed with one or more suitable solvent (s), aqueous and / or organic (s), but preferably aqueous and finally dried between 50 ° C and 150 ° C, according to the usual techniques known to those skilled in the art.

The average size of the crystals may in particular be controlled by adjusting the content of nucleating agent (nucleation gel, or crystals for example of zeolite, or other) relative to the growth gel in step b).

The dried crystals are then subjected to calcination, a step necessary to release both the microporosity (elimination of water) and the mesoporosity (elimination of the structuring agent). The calcination used to eliminate the structuring agent can be carried out according to any calcination method known to those skilled in the art. For example, and in a nonlimiting manner, the calcination of the zeolite crystals comprising the structuring agent can be carried out under an oxidizing and / or inert gas scavenging, with in particular gases such as oxygen, nitrogen, air, a dry air and / or decarbonated, an air depleted oxygen, optionally dry and / or decarbonated, at a temperature or temperatures above 150 ° C, typically between 180 ° C and 800 ° C, preferably between 200 ° C and 650 ° C, for a few hours, for example between 2 and 6 hours. The nature of the gases, the ramps of temperature rise and the successive stages of temperatures, their durations will be adapted according to the nature of the structuring agent.

It would not be outside the scope of the invention by operating one or more cationic exchanges (for example with alkali metal or alkaline earth metal salt (s)), before or after the drying step and / or calcination (step f)), according to conventional cation exchange techniques.

As indicated above, the synthesis method of the invention is easy to implement and it is performed in a relatively short time, and in particular in a reduced time by a factor of at least 4, with respect to methods for the synthesis of ZPH known from the prior art which are very long, for example due to the inhibitory effect of the organosilane structurant for the nucleation and growth of the microporous zeolite network. It has been discovered, quite surprisingly, that the inhibitory effect of the structuring agent (eg TPOAC) is compensated for by the presence of the nucleating agent.

This simplicity and rapidity of synthesis, however, do not affect the quality and properties of zeolites thus obtained. Indeed, thanks to the process of the invention, it is possible to increase the selectivity of the synthesis to a pure zeolite structure (with less than 2% by weight of other crystalline phase (s) pollutant (s) (s)) and to be able to maximize the ratio [microporous volume / mesoporous outer surface] for a given external surface, which is not the case with the methods known from the prior art (see for example the works of Y Meng (ibid.) Shows that an increase in the content of structuring agent, which should lead to an increase in the mesoporous volume, also has the effect of modifying the growth rates of the zeolite network, thus causing the appearance of other zeolitic crystalline phases and thus the formation of mixtures of zeolitic structures, which is not desired).

Indeed, with the processes of the prior art, the increase of the microporous volume of the zeolite and the maintenance of a high phase purity are obtained only by means of very long crystallization times and relatively low temperatures (<80 ° C). These methods, however, never reach microporous volumes comparable to those of the invention. Thus, compared with other processes for preparing ZPH, for example by post-treatment, the process of the invention is more productive and less expensive because it is carried out in a single step, of relatively short duration. (less than one day) with a low amount of structuring agent, and therefore globally with a relatively low cost, or at least with a limited additional cost compared to that of a non-mesoporous zeolite synthesis, and much lower than the cost induced by methods of synthesis of ZPH by post-treatment.

The use of these hierarchically porous zeolites is particularly advantageous in industrial processes such as adsorption, ion exchange, separation, and can also be envisaged in all technical fields in which the non-mesoporous zeolites are usually used.

The present invention is now illustrated by the following examples which are presented without any intention to limit the various embodiments of the invention.

In the following examples, the physical properties of zeolite crystals are evaluated by methods known to those skilled in the art, the main of which are recalled below.

Loss of fire of zeolite crystals

The loss on ignition is determined in an oxidizing atmosphere, by calcination of the sample in air at a temperature of 950 ° C ± 25 ° C, as described in standard NF EN 196-2 (April 2006). The standard deviation of measurement is less than 0.1%.

Volume of Dubinin-Raduskevich:

The volume of Dubinin-Raduskevich is determined from the measurement of the gas adsorption isotherm, such as nitrogen or argon, at its liquefaction temperature, depending on the pore opening. zeolite structure: argon or nitrogen for LTA (previously exchanged with calcium, as described in Breck, ibid., Table 5.7, page 428) and nitrogen for FAU. Prior to adsorption, the zeolite adsorbent is degassed between 300 ° C. and 450 ° C. for a period of between 9 hours and 16 hours under vacuum (P <6.7 × 10 ^-4 Pa). adsorption is then carried out on an ASAP 2020 Micromeritics-type apparatus, taking at least 35 measuring points at relative pressures with a ratio Ρ / Ρ 0 of between 0.002 and 1. The microporous volume is determined according to Dubinin-Raduskevitch from FIG. isotherm obtained by applying the ISO 15901 -3 (2007) standard.The microporous volume evaluated according to the Dubinin-Raduskevitch equation is expressed in cm ³ of liquid adsorbate per gram of zeolite. The measurement uncertainty is ± 0.003 cm ³ .g ^"1 .

Size and morphology of crystals (SEM)

The estimation of the number average diameter of the zeolite crystals is carried out as indicated previously by observation with a scanning electron microscope.

In order to estimate the size of the zeolite crystals on the samples, a set of images is carried out at a magnification of at least 5000. The diameter of at least 200 crystals is then measured using a dedicated software, for example the Smile View software from the LoGraMi editor. The accuracy is of the order of 3%.

The morphology of the crystals is qualified from SEM photos taken at magnification adapted to the size of the crystals.

Measurement of the mesoporous outer surface (m ^2, g ¹ ) by the so-called t-plot method:

The t-plot calculation method exploits the data of the adsorption isotherm Q ads = f (Ρ / Ρ0) and calculates the microporous surface. The mesoporous outer surface can be deduced by differentiating with the BET surface which measures the total porous area in m ² . g ^"1 (S BET = S microp. + S ext. mesop.).

[0066] To calculate the microporous surface by the t-plot method, draw Q ads curve (cm ^3. G ^"1) according to t = thickness of the partial pressure dependent layer Ρ / Ρ0 may form and a non-porous reference solid (t log function Ρ / Ρ0: Harkins equation and applied Jura (ISO 15901 -3: 2007)):

[13.99 / (0.034-log (P / P0)) ^A 0.5],

where in the range t between 0.35 nm and 0.5 nm, a line can be drawn which defines an adsorbed Y intercept which allows the microporous surface to be calculated; if the solid is not microporous the line goes through 0.

Observation of the Mesoporous Structure by Transmission Electron Microscopy

The powder is dispersed in ethanol: 1 minute under ultrasound. One drop of the solution is deposited on a microscopy grid. The sample is allowed to dry at room temperature. The observation is made with a transmission electron microscope (FEI CM 200) at a voltage of 120 kV.

The magnifications obtained from x 220000 (see Figure 1 b) make it possible to visualize the presence of the mesopores and to estimate their diameters.

Analysis of the atomic Si / Al ratio of zeolites by X-ray fluorescence

An elemental chemical analysis of the zeolite with hierarchical porosity can be carried out according to various analytical techniques known to those skilled in the art. Among these techniques, one can quote the technique of chemical analysis by ray fluorescence X as described in standard NF EN ISO 12677: 201 1 on a wavelength dispersive spectrometer (WDXRF), for example Tiger S8 from Bruker.

X-ray fluorescence is a non-destructive spectral technique exploiting the photoluminescence of atoms in the X-ray domain, to establish the elemental composition of a sample. The excitation of the atoms generally by an X-ray beam or by bombardment with electrons, generates specific radiations after return to the ground state of the atom. The X-ray fluorescence spectrum has the advantage of relying very little on the chemical combination of the element, which offers a precise determination, both quantitative and qualitative. A measurement uncertainty of less than 0.4% by weight is obtained conventionally after calibration for each oxide.

These elementary chemical analyzes make it possible to verify the atomic ratio Si / Al of the zeolite, the uncertainty of measurement of the atomic ratio Si / Al is of ± 5%.

Qualitative and quantitative analyzes by X-ray diffraction

This analysis makes it possible to identify the crystalline phases present in the solid analyzed because each of the zeolite structures has a single diffractogram (or diffraction spectrum) defined by the positioning of the diffraction peaks and by their relative intensities.

The zeolite crystals are spread and smoothed on a sample holder by simple mechanical compression. The conditions of acquisition of the diffractogram realized on the device D5000 Brucker are the following ones:

• Cu tube used at 40 kV - 30 mA;

• size of the slots (divergent, diffusion and analysis) = 0.6 mm;

• filter: Ni;

• rotating sample device: 15 rpm ^"1 ;

• measuring range: 3 ° <2Θ <50 °;

• not: 0.02 °;

• counting time in steps: 2 seconds.

The interpretation of the diffraction spectrum (or diffractogram) obtained is carried out with the EVA software with identification of the phases using the ICDD PDF-2 base, release 201 1 which makes it possible to highlight a phase perfectly. crystalline.

The amount of zeolite fractions X is measured by XRD analysis. This analysis is carried out on a device of the Bruker brand, then the quantity of the zeolite fractions X is evaluated using the software TOPAS Bruker society. Example 1

Synthesis of XPH with addition of nucleation gel and growth gel with TPOAC / AI2O3 ratio = 0.04

(where XPH indicates a zeolite with hierarchical porosity (ZPH) type X)

a) Preparation of the growth gel in stirred reactor with Archimedes screw at 300 rpm ^"1 .

In a 3 liter stainless steel reactor equipped with a heating jacket, a temperature probe and a stirrer, a growth gel is prepared by mixing an aluminate solution containing 19 g of hydroxide. sodium (NaOH), 128 g of alumina trihydrate (ΑΙ ₂ 0 ₃ · 3Η ₂ 0 containing 65.2% by weight AI ₂ 0 ₃₎ and 195.5 g water at 25 ° C in 25 minutes with an agitation rate of 300 tr.min ^"1 in a silicate solution containing 565.3 g of sodium silicate, 55.3 g of NaOH and 1997.5 g of water at 25 ° C.

[0077] The stoichiometry of the gel growth is as follows: 3.48 Na ₂ 0 / AI ₂ 0 ₃ / 3.07 Si0 _2/180 H ₂ 0. The homogenization of the gel growth is carried out with stirring at 300 revolutions min ^-1 for 25 minutes at 25 ° C.

b) Addition of the nucleation gel

[0078] To the gel growth at 25 ° C with stirring at 300 tr.min ^"1, 61, 2 g of nucleating gel (2% by weight) of composition 12 Na ₂ 0 / AI ₂ 0 ₃ / 10 Si0 _2/180 H ₂ 0 prepared in the same manner as the growth of frost, and ripened for 1 hour at 40 ° C. After 5 minutes of homogenization at 300 tr.min ^"1, the stirring rate is reduced to 100 r ^"1 and continued for 30 minutes.

c) Introduction into the reaction medium of the structuring agent

27.3 g of 60% TPOAC solution in methanol (MeOH) are introduced into the reaction medium with a stirring speed of 300 rpm ^"1 (TPOAC / Al ₂ 0 ₃ molar ratio = 0). , 04). the process is performed at 25 ° C a soaking step for 1 hour at 300 tr.min ^"1 before starting the crystallization.

d) Crystallization

[0080] It lowers the stirring speed to 50 tr.min ^"1 and the set is fixed to the jacket of the reactor to 80 ° C so that the reaction mixture warms up to 75 ° C in 80 minutes. After 22 at 75 ° C., the reaction medium is cooled by circulating cold water in the jacket to stop the crystallization e) Filtration / washing

The solids are recovered on sintered and then washed with deionized water until neutral pH. f) Drying / Calcination

In order to characterize the product, the drying is carried out in an oven at 90 ° C for 8 hours, the loss on ignition of the dried product is 23% by weight.

The calcination of the dried product necessary to release both the microporosity (water) and the mesoporosity by eliminating the structuring agent is carried out with the following temperature profile: 30 minutes of temperature rise at 200 ° C., then 1 bearing time at 200 ° C, then 3 hours of temperature rise at 550 ° C, and finally 1.5 hours of bearing at 550 ° C.

There is thus obtained 255 g of anhydrous equivalent solid of XPH zeolite; which represents a yield of 99 mol% relative to the amount of aluminum involved. The Si / Al ratio of the X-ray fluorescence ZPH is 1.24.

Example 2

Synthesis of XPH with addition of nucleation gel and growth gel with TPOAC / AI2O3 ratio = 0.02

The procedure is as described in Example 1, with a TPOAC / Al ₂ O ₃ molar ratio of 0.02. 255 g of anhydrous equivalent solid of XPH zeolite are obtained, which represents a yield of 99 mol% relative to the amount of aluminum involved. The Si / Al ratio of the X-ray fluorescence ZPH is 1.24.

Example 3:

Synthesis of XPH with addition of nucleation gel and growth gel with TPOAC / AI2O3 ratio = 0.08

The procedure is as described in Example 1, with a TPOAC / Al ₂ O ₃ molar ratio of 0.08. 255 g of anhydrous equivalent solid of XPH zeolite are obtained, which represents a yield of 99 mol% relative to the amount of aluminum involved. The Si / Al ratio of the X-ray fluorescence ZPH is 1.24.

Example 4:

Synthesis of XPH with addition of zeolite crystals and growth gel with TPOAC / AI2O3 ratio = 0.04

The procedure is as described in Example 1, with a TPOAC / Al ₂ O ₃ molar ratio of 0.04, and in step b) the nucleation gel is replaced by the introduction of 1% by weight. weight (relative to the total weight of the growth gel) of zeolite X crystals (crystals with a mean diameter by volume of about 0.8 μηη, prepared as described in example b) of the synthesis of application WO2014 / 090771). 254 g of a solid having the same characteristics as those obtained for the solid of Example 1 are obtained. Comparison of the characteristics of the zeolite X powders with hierarchical porosity synthesized in Examples 1, 2 and 3

[0088] The results of the characterization of zeolites with a hierarchical porosity are summarized in Table 1 with comparison with a zeolite X reference, the Siliporite ^® G5 AP, sold by the company Ceca, and whose average crystal size is of 1, 5 μηι.

The porosity characteristics (microporous volume, mesoporous outer surface, size distribution of the mesopores) are calculated from the nitrogen adsorption / desorption isotherms at the temperature of the liquid nitrogen of a previously degassed powder at room temperature. 300 ° C under vacuum. Measurements are made on an ASAP 2020 Micromeritics device.

The microporous volume (cm ^3, g ^-1 ) is calculated according to the Dubinin-Radushkevich theory The mesoporous outer surface (m ^2, g ^-1 ) is calculated from the t-plot model. The mesopore size distribution is calculated by the Density Functional Theory (DFT) method with the cylindrical Pore model.

The X-ray diffraction makes it possible to identify the crystalline phases present in the powder from the reference spectra (or diffractograms) of the various zeolite structures and to demonstrate the level of crystallinity of the solids produced as a function of the peak intensity.

FIGS. 1a and 1b show TEM images of the reference zeolite (FIG. 1 a) and the zeolite according to the invention of example 1 (FIG. 1b) and FIG. pores (volume in micropores and volume in mesopores) as a function of pore size. The pore volume is determined as indicated above (measurement from the nitrogen adsorption isotherm as described in the technical section "Dubinin-Raduskevich Volume" supra).

Comparative Example 1: Synthesis of zeolite crystals without addition of nucleation gel, and with TPOAC / Al ₂ O ₃ = 0.04

1) Preparation of the growth gel in stirred reactor with Archimedes screw at 300 rpm ^"1 .

In a 3-liter stainless steel reactor equipped with a heating jacket, a temperature probe and a stirrer, a growth gel is prepared by mixing an aluminate solution containing 19 g of hydroxide. of sodium (NaOH) at 128 g of alumina trihydrate (Al ₂ O ₃ · 3H ₂ O, containing 65.2% by weight of Al ₂ O ₃ ) and 195.5 g of water at 25 ° C. 25 minutes with a stirring speed of 300 tr.min ^"1 in a silicate solution containing 565.3 g of sodium silicate, 55.3 g of NaOH and 1997.5 g of water at 25 ° C. [0094] The stoichiometry of the gel growth is as follows: 3.48 Na ₂ 0 / AI ₂ 0 ₃ / 3.07 Si0 _2/180 H ₂ 0. The homogenization of the gel growth is carried out with stirring at 300 revolutions min ^-1 for 25 minutes at 25 ° C.

2) Introduction into the reaction medium of the structuring agent

27.3 g of 60% TPOAC solution in MeOH are introduced into the reaction medium with a stirring speed of 300 rpm ^"1 (TPOAC / Al ₂ O ₃ molar ratio = 0.04). After 5 minutes of homogenization, the stirring speed is lowered to 50 rpm ^"1 .

3) Ripening phase

The stirred reaction medium is maintained at 50 rpm ^"-1 at 25 ° C for 22 hours, then the crystallization is started.

4) Crystallization

The stirring speed is maintained at 50 rpm ^"-1 , and the set point of the jacket of the reactor is set at 80 ° C. so that the reaction medium rises to 75 ° C. in 80 minutes. 72 hours of residence at 75 ° C, the reaction medium is cooled by circulating cold water in the jacket to stop crystallization.

5) Filtration / washing

The solids are recovered on sintered and then washed with deionized water until neutral pH.

6) Drying / Calcination

In order to characterize the product, the drying is carried out in an oven at 90 ° C for 8 hours, the loss on ignition of the dried product is 22% by weight.

The calcination of the dried product necessary to release both the microporosity (water) and the mesoporosity by eliminating the structuring agent is carried out with the following temperature profile: 30 minutes of rise at 200 ° C., then 1 hour of bearing at 200 ° C, then 3 hours of rise at 550 ° C, and finally 1.5 hours of bearing at 550 ° C.

Comparative Example 2

Synthesis of zeolite crystals without addition of nucleation gel, and with TPOAC / Al2O3 = 0.08

The procedure is as described in Comparative Example 1, increasing the molar ratio TPOAC / Al ₂ O ₃ to 0.08.

Comparison of characteristics of zeolite powders with hierarchical porosity synthesized in Comparative Examples 1 and 2 with zeolites of ex. 1, 2 and 3.

The results of the characterizations of zeolites with hierarchical porosity are summarized in Table 1 below: - Table 1 -

Legend:

SEM: scanning electron microscopy

MET: Transmission Electron Microscopy

Reference: CECA X Siliporite ^® G5 AP zeolite

νμρ: microporous volume calculated with Dubinin-Raduskevitch equation

S ext. mésop. : mesoporous external surface deduced from the extrapolation t-plot.

The results presented in Table 1 above show that the morphology of the crystals varies with the TPOAC content. One explanation is the effect of the structuring agent on the growth rates of the different crystal faces.

Figure 3 shows the superposition of the diffraction spectra (diffractograms). The superposition of the X-ray diffraction spectra (diffractograms) shows that the intensities of the diffraction peaks obtained with the solids according to the invention (zeolite of Example 1, referenced (b) in FIG. 3) are similar to those obtained. with the reference zeolite (referenced (a) in Figure 3), regardless of the amount of structuring agent introduced. The method according to the invention thus makes it possible to obtain solids whose crystallinity is optimal and controlled.

The synthesis method implemented with the use of a structuring agent, a seeding gel and / or a nucleation gel makes it possible to vary the microporous volume / mesoporous outer surface distribution in the case of zeolites with a low Si / Al ratio, typically between 1 and 1, 4, while obtaining a pure FAU (Faujasite) type zeolite, without observing any other crystalline form, and in particular without co-crystallization of P. zeolite.

Example 5

Synthesis of XPH with addition of nucleation gel and growth gel with TPOAC / Al ₂ O ₃ ratio = 0.04

The procedure is as described in Example 1, with the addition of 10% by weight of the same nucleating gel with respect to the weight of the growth gel so as to reduce the size of the crystals.

The zeolite obtained has a crystal size of between 0.5 and 1.0 μm, that is to say less than the size of the crystals of the zeolite obtained in Example 1.

Example 6

Synthesis of LSXPH with addition of nucleation gel and growth gel with TPOAC / Al ₂ O ₃ ratio = 0.04.

a) Preparation of the growth gel: reactor stirred by Archimedes screw at 250 rpm ^"1 .

In a 3 liter stainless steel reactor equipped with a heating jacket, a temperature probe and a stirrer, a growth gel is prepared by mixing an aluminate solution containing 300 g of sodium hydroxide. sodium (NaOH), 264 g of 85% potassium hydroxide, 169 g of alumina trihydrate (Al ₂ O ₃ , 3H ₂ O, containing 65.2% by weight of Al ₂ O ₃ ) and 1200 g water at 25 ° C in 5 minutes with a speed stirring 250 tr.min ^"1 silicate with a solution containing 490 g of sodium silicate, 29.4 g of NaOH and 470 g of water at 25 ° C.

[0109] The stoichiometry of the gel growth is as follows: 4.32 Na ₂ 0/1 85 K ₂ 0 / AI ₂ 0 ₃ / Si0 ₂ 2.0 / 1 14H ₂ 0. The homogenization of the gel growth is carried out with stirring at 250 tr.min ^"1 for 15 minutes at 25 ° C.

b) Addition of the nucleation gel

[0110] To the gel growth at 25 ° C with stirring at 300 tr.min ^"1, 5.8 g of nucleating gel (0.2 wt%) of composition 12 Na ₂ 0 / AI ₂ 0 _3/10 Si0 _2/180 H ₂ 0 prepared in the same manner as the growth of frost, and ripened for 1 hour at 40 ° C. After 5 minutes of homogenization at 250 tr.min ^"1, the rate of agitation is reduced to 50 tr.min ^"1 and continued for 30 minutes.

c) Introduction into the reaction medium of the structuring agent

[0111] are introduced into the reaction mixture 35.7 g of 60% TPOAC solution in methanol (MeOH) with an agitation speed of 250 tr.min ^"1 for 5 minutes (molar ratio TPOAC / AI ₂ 0 ₃ = 0.04). Then the reaction is carried at 30 ° C a ripening step for 20 hours at 50 tr.min ^"1 before starting the crystallization.

d) Crystallization in 2 steps

Maintaining the stirring speed at 50 rpm ^"1 and then an increase in the set point of the reactor jacket to 63 ° C linearly so that the reaction medium temperature increases to 60 ° C in 5 hours followed by a 21 hour stage at 60 ° C., then the set point of the jacket of the reactor is set at 102 ° C. so that the reaction medium rises to 95 ° C. in 60 minutes. at 95 ° C, the reaction medium is cooled by circulating cold water in the jacket to stop the crystallization.

e) Filtration / washing

The solids are recovered on sintered and then washed with deionized water to neutral pH.

f) Drying / Calcination

In order to characterize the product, the drying is carried out in an oven at 90 ° C. for 8 hours.

The calcination of the dried product necessary to release both the microporosity (water) and the mesoporosity by eliminating the structuring agent is carried out by vacuum degassing with a gradual increase in steps of 50 ° C. to 400 ° C. C for a period of between 9 hours and 16 hours under vacuum (P <6.7 × 10 ^-4 Pa).

The results of the characterizations of this zeolite with hierarchical porosity are: - microporous V Dubinin-Raduskevich = 0.278 cm ³ . g ^"1

- S ext. mésop. = 97 m ² . g ^"1

- Diameters of the mesopores DFT = 5 nm to 10 nm.

- X-ray diffractogram: pure Faujasite structure, no LTA zeolite detected.

- Crystal size: 8 μηι

The Si / Al molar ratio of the LSXPH determined by X-ray fluorescence is equal to 1.11.

Example 7

Synthesis of zeolite APH with addition of nucleation gel and growth gel with TPOAC / Al ₂ O ₃ ratio = 0.04.

a) Preparation of the growth gel

[0117] In glass reactor of 1, 5 liters stirred with a 3-blade propeller 600 tr.min ^"1 provided with a heating mantle and a temperature sensor; a growth gel is prepared by mixing a aluminate solution containing 151 g of sodium hydroxide (NaOH), 1 12.4 g of alumina trihydrate (ΑΙ ₂ 0 ₃ · 3Η ₂ 0 containing 65.2% by weight AI ₂ 0 ₃₎ and 212 g water at 35 ° C in 5 minutes with a stirring speed of 600 tr.min ^"1 silicate with a solution containing 321 4 g of sodium silicate and 325 g of water at 35 ° C.

[0118] The stoichiometry of the gel growth is as follows: 3.13 Na ₂ 0 / AI ₂ 0 _3/1, 92 Si0 _2/68 H ₂ 0. The homogenization of the gel growth is carried out with stirring at 600 rev .min ^"1 for 15 minutes at 35 ° C.

b) Addition of the nucleation gel

[0119] To the gel growth at 35 ° C with stirring at 300 tr.min ^"1, 1 1, 2 g of nucleating gel (1% by weight) composition of 2.05 Na ₂ 0 / Al ₂ 0 _3/1, 92 Si0 _2/87 H ₂ 0 prepared in the same manner as the growth of frost, and ripened for 2 hours at 25 ° C. After 5 minutes of homogenization at 300 tr.min ^"1, the stirring speed was decreased to 190 tr.min ^"1 and continued for 30 minutes.

c) Introduction into the reaction medium of the structuring agent

35.7 g of 60% TPOAC solution in methanol (MeOH) are introduced into the reaction medium with a stirring speed of 600 rpm ^" (TPOAC / Al ₂ O ₃ molar ratio = 0). , 04). the process is performed at 35 ° C a ripening step for 10 minutes at 300 tr.min ^"1 before starting the crystallization.

d) Crystallization

[0121] It lowers the stirring rate at 190 tr.min ^"1 and the set is fixed to the jacket of the reactor to 105 ° C so that the reaction mixture warms up to 97 ° C in 40 minutes. After standing for 3 hours at 97 ° C., the reaction medium is cooled by circulating cold water in the jacket to stop the crystallization. e) Filtration / washing

f) Drying

The drying is carried out in an oven at 90 ° C. for 8 hours to obtain a solid with a loss on ignition of 20%.

g) Calcium exchange

In order to characterize the porosity of the APH zeolite, calcium exchange is performed to obtain a diameter of the micropores of about 0.5 nm: 50 g of dried powder are brought into contact with 500 cm ³ of CaCl ₂ 0.5 M solution at 70 ° C for 2 hours then filtered and washed with 280 mL of water. The operation is repeated 3 times (triple exchange).

h) Drying

i) Calcination

The results of the characterizations of this zeolite with a hierarchical porosity CaAPH are as follows:

- microporous V Dubinin-Raduskevich = 0.265 cm ³ . g ^"1

- S ext. mésop. = 102 m ² . g ^"1

- Diameters of the mesopores DFT = 5 nm to 10 nm.

- RX diffractogram: pure LTA zeolite structure.

- Size of the crystals: 0.8 μηι.

The Si / Al molar ratio of the HPA determined by X-ray fluorescence is equal to 1.02.

The method described in the present invention is economically viable, simple to implement on an industrial scale, with a very significant time saving compared to the syntheses described in the prior art. In addition, the synthesis process of the invention makes it possible to achieve quite satisfactory yields, for example with an optimum yield of 99% relative to the amount of aluminum involved and which is the element in default in the gel. of synthesis.

Claims

1. A hierarchically porous zeolite having at least the following characteristics:

• molar ratio Si / Al of between 1 and 1, 4, limits included,

• controlled and optimal crystallinity, and

Mesoporosity such that the mesoporous outer surface is between 40 m ² . g ^"1 and 400 m ² .g ^-1 , preferably between 60 m ² .g ^-1 and 200 m ² .g ^-1 .

2. The zeolite according to claim 1, which is a zeolite of the FAU type, and in particular an X, MSX, LSX zeolite or an EMT zeolite or an LTA zeolite.

Zeolite according to Claim 1 or Claim 2, comprising a pure zeolitic phase, and on the other hand a microporous volume νμρ corresponding to the equation νμρ = νμρ _κ ± 15%, preferably to the equation νμρ = \ μρ _κ ± 10%, more preferably to the equation νμρ = \ μρ _κ ± 5%, where \ / μρ _κ represents the microporous volume measured, under the same conditions, for a zeolite of the same chemical nature and with the same crystalline structure, but not mesoporous within the meaning of the invention, that is to say whose mesoporous outer surface is strictly less than 40 m ² . g ^"1 .

4. Process for the preparation of a zeolite according to any one of the preceding claims, comprising at least the following steps:

c) adding to the reaction medium at least one structuring agent,

d) crystallization reaction by increasing the temperature,

e) filtration and washing of the zeolite crystals obtained, and

f) drying and calcination.

The method of claim 4, wherein the nucleating agent is a nucleation gel.

The process according to any one of claims 4 or 5, wherein the amount of nucleation gel added is between 0.1% and 20%, preferably between 0.5% and 15% by weight, more preferably between 1% and 10% by weight, limits included, relative to the weight of the growth gel.

The method of claim 4, wherein the nucleating agent is a crystal.

The method of any one of claims 4 or 7, wherein the amount of added crystal is from 0.1% to 10% by weight based on the total weight of growth gel.

The process of any one of claims 4 to 8, wherein the source of silica is sodium silicate, and the source of alumina is alumina trihydrate.

The process according to any one of claims 4 to 9, wherein the structuring agent is an organosilane.

11. Process according to any one of claims 4 to 10, in which the structuring agent is chosen from [3- (trimethoxysilyl) propyl] octadecyldimethylammonium chloride, [3- (trimethoxysilyl) propyl] hexadecyldimethylammonium chloride. [3- (trimethoxysilyl) propyl] dodecyldimethylammonium chloride, [3- (trimethoxysilyl) propyl] octylammonium chloride, N- [3- (trimethoxysilyl) propyl] aniline, 3- [2- (2-aminoethylamino) ) ethylamino] propyltrimethoxysilane, N- [3- (trimethoxysilyl) propyl] -N '- (4-vinylbenzyl) ethylenediamine, triethoxy-3- (2-imidazolin-1-yl) propylsilane, 1 - [3- ( trimethoxysilyl) propyl] urea, N- [3- (trimethoxysilyl) propyl] ethylenediamine, [3- (diethylamino) propyl] trimethoxysilane, (3-glycidyloxypropyl) trimethoxysilane, 3- (trimethoxysilyl) propyl methacrylate, [2- (cyclohexenyl) ethyl] triethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, (3-aminopropyl) trimethoxysilane, (3-mercaptopropyl) trimethoxysilane, (3-chloropropyl) trimethoxysilane, as well as mixtures of two or more of them in all proportions.

12. Method according to any one of claims 4 to 1 1, wherein the amount of structuring agent (s) is such that the molar ratio of agent (s) structurant (s) / AI ₂ 0 ₃ starting is between 0.005 and 0.20, preferably between 0.01 and 0.15, more preferably between 0.02 and 0.08 inclusive.