FR3058072A1 - PROCESS FOR THE PREPARATION OF A POROUS COMPOSITE MATERIAL - Google Patents

Abstract

The invention describes a process for preparing a composite porous material comprising at least one zeolite and at least one alumina precursor, said process comprising at least the following steps: a) a step for obtaining zeolite crystals in suspension in the synthesis reaction medium, b) at least one step of precipitating at least one precursor of alumina in the suspension obtained at the end of step a), by contacting at least one precursor aluminum acid.

Description

Technical area

The invention relates to a process for the preparation of a porous composite material based on an alumina and zeolite precursor, which can be shaped in the form of extrudates, beads or tablets, and which can be used as a catalyst. , catalyst support or as adsorbent, for different applications. The composite porous material obtained having the specificity of being porous micro-, meso- and macroporous and of presenting a particular acidity, it may be used, in particular for hydrocracking catalysis, isomerization catalysis and all other applications requiring such properties.

Prior art

In general, porous materials comprising zeolite and an alumina precursor are obtained by mixing two powders, one of zeolite and one of alumina precursor, prepared according to two separate preparation processes.

The synthesis of said powders is carried out separately and requires numerous unitary steps such as, filtration, washing, drying and possibly calcination.

More particularly, the synthesis of zeolite powders is carried out in at least one precipitation step, preferably in an aqueous reaction medium using at least one source of silicon atoms and optionally at least one source of aluminum atoms, the all in basic medium in the presence of organic or inorganic structuring agents.

More particularly, the synthesis of alumina precursor powders is carried out in at least one stage of precipitation, in an aqueous reaction medium, of at least one basic precursor chosen from sodium aluminate, potassium aluminate, ammonia, sodium hydroxide and potassium hydroxide and at least one acid precursor chosen from aluminum sulphate, aluminum chloride, aluminum nitrate, sulfuric acid, hydrochloric acid , and nitric acid, in which at least one of the basic or acidic precursors comprises aluminum.

The conventional methods for preparing porous composite materials have several drawbacks. One of them is that the zeolite and the alumina precursor are introduced in the form of more or less dispersible powders, which leads to the production of a heterogeneous product having zeolite islands of micron size.

It is known that the dilution of the zeolite in the alumina precursors leads to a reduction in the acidity of said zeolite, which is accompanied by a reduction in the number of acid sites per gram of catalyst.

Indeed, the accessibility to the acid sites of the zeolite is modified by the binder. The micropores of the zeolite can be blocked by the binder nanocrystals, this is a phenomenon called according to English terminology "binder-blinding". This is the main problem when shaping a zeolite. If the microporosity is completely or partially blocked, access to the active sites is no longer possible or greatly reduced and the activity of the catalyst composed of zeolite is then reduced. Furthermore, it is known that the various additives which are added to the zeolite during this shaping step alter the properties of said zeolite (AdvFunctMater 2012, 22, 2509; ACSCatal 2014, 4, 2409).

Surprisingly, the Applicant has discovered a process for preparing a porous composite material composed of a mixture of zeolite and alumina precursor whose distribution is perfect. By perfect is meant a homogeneous and intimate mixture of zeolite and alumina precursor crystals. Said method makes it possible to overcome all the problems associated with the preparation by mixing powder of alumina precursor and zeolite.

Definition and Abbreviations

An alumina precursor is defined as an aluminum trihydroxide (mainly called bayerite or gibbsite) or an aluminum oxy-hydroxy (mainly boehmite) or even amorphous alumina leading after a calcination and therefore dehydration step to a transition alumina. The alumina phase obtained will depend on the calcination temperature applied, the most stable thermodynamic phase being the most stable and which is obtained for a calcination close to 1000 ° C. The phase most used in catalysis is gamma alumina, obtained for calcination between 500 and 700 ° C of an alumina precursor as defined above.

By homogeneous and intimate mixture is meant a powder composed of both zeolite crystals and alumina precursor which are difficult to discriminate and to identify by simple analysis by electron microscopy.

The term “transition alumina” is understood to mean the different phases of alumina obtained by calcination of an alumina precursor until the thermodynamically most stable alumina is obtained. The nature of the transition alumina obtained is determined by the calcination temperature.

Subject of the invention

The present invention relates to a process for the preparation of a porous composite material comprising at least one zeolite and at least one alumina precursor, said process comprising at least the following steps:

a) a step for obtaining zeolite crystals in suspension in the synthetic reaction medium,

b) At least one step of precipitation of at least one acid precursor of alumina by bringing the suspension obtained at the end of step a) into contact.

An essential criterion of the process according to the invention is that part or all of the basic precursor used for the precipitation of the alumina precursor is the suspension of zeolite crystals in its synthetic reaction medium resulting from step a).

An advantage of the invention is the elimination of the stages of filtration, washing, drying and calcination during the synthesis of the zeolite crystals, which represents a significant economic gain, for the implementation of the process on an industrial scale.

Another advantage of the invention is that it makes it possible to overcome the phenomenon of aggregation of zeolite crystals during the filtration-washing, drying and calcination stages. In fact, the process of the invention makes it possible to optimize the dispersion of the zeolite crystals in the alumina precursor and to keep the particle size of the zeolite in suspension in the reaction medium at the outlet of the synthesis until the shaping composite porous material. The conservation of the particle size is accompanied by a homogeneous dispersion of the zeolite in the alumina precursor. This state of dispersion is advantageously kept until the final product obtained by said process. This is characterized by electron microscopy.

Another advantage of the process according to the invention is that it allows the porosity of the zeolite obtained in step a) to be preserved in the zeolite of the porous material after precipitation of the alumina precursor. The porosity thus obtained is of particular interest for the catalytic activity and for the separation of the porous material.

Another advantage of the invention is to be able to carry out the precipitation of the alumina precursor without adding base, which represents a significant economic and ecological gain.

Another advantage of the process of the invention is that it makes it possible to obtain powder of different formulation which may contain up to 95% by weight of zeolite.

Detailed description of the invention

In the sense of the present invention, the various embodiments presented can be used alone or in combination with each other, without limitation of combination.

Step a) obtaining zeolite crystals

According to the invention, the process for preparing the porous composite material comprising at least zeolite and at least alumina precursor comprises at least one step a) for obtaining zeolite crystals in suspension in the synthesis reaction medium .

Step a) preferably includes a reaction step in an aqueous mixture:

- at least one source of at least one XO ₂ oxide,

- optionally at least one source of at least one oxide Y ₂ O ₃ ,

at least one basic source of at least one alkali and / or alkaline-earth metal M of valence n, and / or

- at least one organic species R comprising one or more quaternary nitrogen atoms.

Preferably, the zeolite crystals obtained in step a) have a chemical composition expressed on an anhydrous basis, in terms of moles of oxides, defined by the following general formula (I): 1XO ₂ : aY ₂ O ₃ : £> M _{2 / n} O, in which

X represents at least one tetravalent element,

Y represents at least one trivalent element and

M is at least one alkali metal and / or one alkaline earth metal of valence n.

Preferably, X is at least one element, tetravalent, chosen from silicon, germanium, titanium and the mixture of at least two of these tetravalent elements, very preferably X is silicon.

Preferably, Y is at least one trivalent element chosen from aluminum, boron, iron, indium and gallium, very preferentially Y is aluminum.

Preferably, M is at least one alkali metal and / or an alkaline earth metal, chosen from lithium, sodium, potassium, calcium, magnesium and the mixture of at least two of these metals and very preferably M is sodium.

Preferably, the reaction medium comprises an organic species, denoted R, comprising at least one quaternary nitrogen atom or one phosphorus atom. Preferably R is chosen from tetrapropylammonium bromide, tetrapropylammonium hydroxide, 18-crown-6 ether, hexamethonium dibromide, tetraethylammonium hydroxide, ethylene diamine, 2,6-dimethylpiperidine.

Preferably the mixture has the following composition:

XO ₂ / Y ₂ O ₃ : at least 2, preferably at least 10, more preferably from 50 to 600, H ₂ O / XO ₂ : 1 to 1000, preferably from 10 to 450,

R / XO ₂ : 0.02 to 2, preferably 0.05 to 0.5,

M _{2 / n} O / XO ₂ : 0 to 1, preferably 0.005 and 0.5,

Where X, Y, R and M have the above meanings.

It may be advantageous to add seeds to the reaction mixture in order to reduce the time necessary for the formation of the crystals and / or the total duration of crystallization. Preferably, the seeds are added during the reaction in an aqueous mixture in step a). It may also be advantageous to use seeds in order to promote the formation of zeolite crystals to the detriment of impurities. Such seeds include crystallized solids, in particular crystals of the desired zeolite. The crystalline seeds are generally added in a proportion of between 0.01 and 10% of the mass of the oxide XO ₂ used in the reaction mixture. Preferably, in a proportion of between 1 and 5%.

The amounts of said reagents are adjusted so as to give the reaction mixture a composition allowing its crystallization into zeolite crystals of the desired structure in its raw synthetic form of general formula (I) XO ₂ : aY ₂ O ₃ : bM _{2 / n} O: cR: dH ₂ O, where a, b, c and d meet the criteria defined below when c and d are greater than 0.

In said formula (I), a represents the number of moles of Y ₂ O ₃ and a is between 0 and 0.5, very preferably between 0.0025 and 0.1 and even more preferably between and 0.005 and 0.1 and b represents the number of moles of M ₂ / _n 0 and is between 0 and 1, preferably between 0.005 and 0.2 and even more preferably between 0.01 and 0.2.

c represents the number of moles of R and is between 0 and 2, preferably between 0 and 1.

Preferably, step a) comprises a hydrothermal treatment of the mixture obtained. Preferably, said hydrothermal treatment is a crystallization. Said hydrothermal treatment is carried out at an autogenous reaction pressure, at a temperature between 40 ° C and 200 ° C, preferably between 80 ° C and 180 ° C, and even more preferably between 85 and 175 ° C up to the formation of solicfe crystals of porous material in its raw synthetic form. The time required to obtain crystallization generally varies between 1 hour and several months depending on the composition of the reactants in the gel, the stirring and the reaction temperature. Preferably the duration of the hydrothermal treatment varies between 2 hours and 21 days. The reaction is generally carried out with stirring or in the absence of stirring, preferably in the presence of stirring. The pH of the zeolite suspension at the end of step a) is between 9 and 14, preferably between 11 and 13.5 and very preferably between 12 and 13.5.

It is up to the knowledge of a person skilled in the art that the reaction conditions used in step a) determine the nature of the zeolite crystals obtained. The zeolite crystals obtained at the end of step a) are chosen from all the zeolites obtained in basic medium known to those skilled in the art and preferably the zeolites of structural type FAU, BEA, ISV, IWR, IWW , MEI, UWY, MFI, FER, EUO, MOR, LTA, EMT, UTL taken alone or in mixture and preferably among the zeolites of structural type FAU, MFI, MOR, FER and BEA, taken alone or in mixture. Said zeolites are defined in accordance with the classification “Atlas of Zeolite Framework Types, 6th revised edition”, Ch. Baerlocher, L. B. Mc Cusker, D.H. Oison, 6th Edition, Elsevier, 2007, Elsevier. Preferably, the zeolite crystals obtained are of the Y zeolite, X zeolite, beta, ITQ-7, ITQ-24, ITQ-22, ZSM-18, IM-12, ZSM-5, silicalite-1, ferrierite, EU type. -1, ZSM-50, mordenite, zeolite A, EMC-2. Very preferably, the zeolite crystals obtained are of the zeolite Y, zeolite X, beta, ZSM-5, silicalite-1, ferrierite, EU-1, ZSM-50, mordenite, zeolite A, EMC-2 type.

Precipitation step b)

According to the invention, the process for preparing a porous composite material comprising at least one zeolite and at least one alumina precursor comprises at least one step b) of precipitating the alumina precursor in the suspension obtained at the end of step a), by bringing at least one acidic aluminum precursor into contact. The suspension resulting from stage a) is the basic precursor allowing the precipitation of the aluminum acid precursor into the alumina precursor.

Preferably, the aluminum acid precursor is chosen from all the aluminum acid precursors known to a person skilled in the art, and preferably from aluminum sulphate, aluminum chloride, aluminum nitrate. Very preferably, the acidic aluminum precursor is aluminum sulphate and aluminum nitrate.

Preferably, the precipitation step b) is carried out in the presence of at least one additional basic precursor, chosen from sodium aluminate, potassium aluminate, ammonia, sodium hydroxide and hydroxide. potassium. Preferably, the additional basic precursor is chosen from sodium aluminate and potassium aluminate. The preferred additional basic precursor is sodium aluminate. The addition of an additional basic aluminum precursor advantageously makes it possible to increase the content of alumina precursor formed.

Preferably, the aluminum acid precursor (s) and the additional basic precursor (s) are added in aqueous solutions in said precipitation step b). Preferably, the suspension obtained in step a) is added simultaneously to the aluminum acid precursor (s). Preferably the additional basic precursor (s) is added simultaneously to the aluminum acid precursor (s) in the suspension obtained in step a). Preferably the suspension obtained in step a), the aluminum acid precursor (s) and the additional basic precursor (s) are added simultaneously.

Preferably, said step b) operates with stirring.

Preferably step b) of precipitation is carried out so as to obtain a reaction medium of between 7 and 12, preferably between 8 and 10.5, preferably between 8.5 and 9.9, operating at a temperature between 10 and 80 ° C, preferably 70 ° C, and for a period between 2 minutes and 50 minutes and preferably 30 minutes.

The additional acid and basic precursors are also mixed in amounts making it possible to obtain a suspension containing the desired amount of alumina precursor, as a function of the final concentration of transition alumina to be reached. In particular, when a second precipitation step is carried out, said step b) makes it possible to obtain 40 to 100% by weight of alumina precursor in equivalent AI ₂ O ₃ relative to the total amount of alumina precursor formed at the end of said precipitation steps.

Second step b ’) optional precipitation

Preferably, the preparation process comprises a second precipitation step bj after the first precipitation step b) and makes it possible to increase the proportion of alumina precursor produced. Said second step bj is carried out by adding to the suspension obtained at the end of step b) at least one additional basic precursor chosen from sodium aluminate, potassium aluminate, ammonia, sodium hydroxide and potassium hydroxide and optionally at least one acid precursor chosen from aluminum sulphate, aluminum chloride, aluminum nitrate, the addition of acid and basic precursors is chosen so to obtain a pH of the reaction medium between 7 and 12, preferably between 8 and 10.5 and preferably between 8.5 and 9.9 and said step bj operating at a temperature between 40 and 90 ° C, and for between 2 minutes and 50 minutes.

Preferably, the addition of acid precursor and / or additional basic precursor to the suspension obtained in step b) is carried out simultaneously. In particular, step bj makes it possible to obtain 0 to 60% by weight of alumina precursor in AI ₂ O ₃ equivalent relative to the total amount of alumina precursor formed at the end of the step or steps of precipitation.

Preferably, at the end of steps b) and bj, the amount of alumina precursor formed is between 20 and 150 g / L and very preferably between 30 and 100 g / L.

Preferably, a ripening step can be carried out after one of the precipitation steps b) or bj. Preferably, said ripening step operates at a temperature between 65 and 150 ° C, preferably between 65 and 130 ° C, preferably between 70 and 110 ° C, very preferably between 70 and 95 ° C and during a duration of between 40 minutes and 5 hours, preferably between 40 minutes and 3 hours and preferably between 45 minutes and 2 hours.

Stage c) of filtration

Preferably, the process for preparing the porous composite material can also comprise a step c) of filtration of the suspension obtained at the end of step b) or b ’) of precipitation. Said filtration step is advantageously carried out according to methods known to those skilled in the art.

Said filtration step is followed by one or more washes of the cake obtained, with an aqueous solution, preferably water. The temperature of the washing solution is preferably between 20 and 70 ° C.

Step d) drying

Preferably, the process for preparing the porous composite material can also include a step d) of drying the cake obtained at the end of step c). Said drying step can be carried out by any means known to those skilled in the art. Preferably step d) of drying is carried out in a closed and ventilated oven, preferably at a temperature between 80 and 120 ° C. Preferably, at the end of the drying, the cake obtained is ground into powder by any method known to a person skilled in the art.

The powder of composite porous material obtained in step d) comprising at least zeolite and an alumina precursor can be characterized by X-ray diffractions.

Step e) of Formatting

Preferably, the method according to the present invention also comprises a step of shaping the powder obtained at the end of step d) of drying to obtain a formed porous composite material. Preferably, said shaping step e) is carried out by extrusion kneading, by tableting, by the oil-drop method, by atomization, by granulation on a turntable or by any other known method of l skilled in the art. Very preferably, said shaping step is carried out by extrusion kneading.

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Step e) of shaping can advantageously be carried out in the presence of at least one additive chosen from paraffins, and polymers, taken alone or as a mixture. Preferably, said additive (s) is chosen from methylcellulose, Cerfobol30 R75, polysaccharides, methylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, carboxymethylcellulose and polyvinyl alcohol taken alone or as a mixture.

Step e) of shaping can advantageously be carried out in the presence of a binder, chosen from boehmite, clays, silicas and aluminophosphates. In the case where step e) of shaping is carried out directly on the powder obtained at the end of step d), the alumina precursor contained in said powder serves as a binder.

Stage f) of calcination

The porous composite material resulting from stage d) or e) can optionally then undergo at least one stage f) of calcination at a temperature of between 500 and 1000 ° C., for a period of between 2 and 10 h, in the presence or not from an air flow containing up to 100% volume of water.

Preferably, step f) of calcination is carried out after step e) of forming the porous composite material.

Said calcination step f) allows the transition from the alumina precursor to the final transition alumina and the adjustment of the textural properties and the properties of the zeolite.

Before or after the heat treatment, said shaped porous composite materials can undergo cationic exchanges, for example with ammonia in order to partially or completely transform the zeolite into its acid form. These treatments are followed by a new calcination at temperatures between 400 and 800 ° C.

The composite porous material obtained in step f) comprises at least zeolite and transition alumina and can be characterized by X-ray diffractions.

The size of the zeolite crystallite agglomerates is analyzed by scanning electron microscopy (SEM), in particular, the average size of the zeolite crystallite agglomerates is determined from scanning electron microscopy (SEM) images using SMile View software. SEM images must be taken in fracture mode and with a secondary electron detector. The size of the zeolite crystallite agglomerates is calculated from the average of the diameters determined over a number of measurements that those skilled in the art deem necessary and sufficient to obtain a statistically representative result and preferably, over at least 50 measurements .

Preferably, the composite porous material shaped and prepared by the above process has:

- a specific surface S _B and greater than 100 m ² / g, preferably between 100 and 900 m ² / g

- a mesoporous median diameter in volume greater than or equal to 7 nm, preferably between 8 and 50 nm

- a mesoporous volume as measured by porosimetry by mercury intrusion, between 0.10 ml / g and 1.10 ml / g, preferably between 0.3 ml / g and 1.0 ml / g

- a microporous volume as measured by nitrogen adsorption isotherm, between 0.01 ml / g and 0.33 ml / g, preferably between 0.02 and 0.25 ml / g

- a total pore volume measured by mercury porosimetry greater than or equal to 0.3 ml / g, preferably between 0.4 and 1.4 ml / g

In a particular embodiment of the invention, the method comprises steps a) and b), or steps a), b) and b '), or steps a), b), and c), or steps a ), b), b ') and c), or steps a), b), c) and d), or steps a), b), b'), c) and d), or steps a ), b), c), d), and e), or steps a), b), b '), c), d), and e), or steps a), b), c), d), e) and f), or steps a), b), b '), c), d), e) and f), or steps a), b), c), d), f ) and e), or steps a), b), b '), c), d), f) and e).

In a particular embodiment of the invention, the method consists of steps a) and b), or steps a), b) and b '), or steps a), b), and c), or steps a), b), b ') and c), or steps a), b), c) and d), or steps a), b), b'), c) and d), or steps a), b), c), d), and e), or steps a), b), b '), c), d), and e), or steps a), b), c) , d), e) and f), or steps a), b), b '), c), d), e) and f), or steps a), b), c), d), f) and e), or steps a), b), b '), c), d), f) and e).

The porous composite material obtained, before shaping, by the process according to the invention is composed of at least one zeolite and at least one alumina precursor, or a transition alumina if a calcination step is carried out, said material porous composite preferably comprising:

- 1 to 90% by weight, preferably from 5 to 70% by weight, even more preferably from 10 to 60% by weight, and very preferably 10 to 50% by weight of zeolite relative to the total mass of said porous composite material,

- 10 to 99% by weight, preferably 30 to 95%, preferably 40 to 90% by weight, and very preferably 50 to 90% by weight in alumina precursor or in transition alumina after calcination relative to the total mass of said material.

List of Figures

Figure 1. X-ray diffractogram (XRD) of zeolite Y from suspension S1 (Example 1) which was washed and calcined at 500 ° C for 4 hours.

Figure 2. X-ray diffractogram (XRD) of the ground B1 extrudates (Example 1).

Figure 3. SEM image of the zeolite Y crystals after shaping step e) (Example 1).

Figure 4. SEM image of the agglomerates of Y zeolite crystals after drying step d) (Example 2).

Figure 5. SEM image of the agglomerates of Y zeolite crystals after step e) of shaping (Example 2). A: zeolite crystals, B: gamma alumina.

Figure 6. X-ray diffractogram (XRD) of the zeolite ZSM-5 from the suspension S3 (Example 3) which was washed and calcined at 500 ° C for 4 hours.

Figure 7. X-ray diffractogram (XRD) of the crushed B3 extrudates (Example 3).

Figure 8. X-ray diffractogram (XRD) of the ground B4 extrudates (Example 4).

Figure 9. X-ray diffractogram (XRD) of the ground B5 extrudates (Example 5).

Figure 10. X-ray diffractogram (XRD) of the crushed B6 extrudates (Example 6).

Figs 1,2 and 5 to 10 are SEM images with the "relative intensity" on the ordinate and the angle 2 theta on the abscissa.

Examples

The examples below illustrate the invention without limiting its scope.

Example 1 Preparation of Extruded Y Zeolite - Gamma Alumina (According to the Invention)

1- Synthesis of the zeolite Y

The composition of the synthesis gel is: 1.33 Na ₂ O / Al ₂ O ₃ 0.133 / 0.8 SiO _2/40 H ₂ O.

224 g of sodium hydroxide are dissolved in 1104 g of permuted water with stirring. The mixture obtained is called mixture C1.

118 g of aluminum isopropoxide are dissolved in the mixture C1 with stirring at 300 rpm and the mixture is kept with a cover for 90 minutes. Then, the cover is removed to allow the evaporation of the alcohols formed (12 hours). Then, the mass is completed with water permuted losses up to the expected mass. The mixture obtained is called mixture D1.

641 g of colloidal suspension of silicon (equivalent to 103 g SiO ₂ ) are added to the mixed D1 drop by drop using a pump. The gel obtained is strongly stirred for 5 minutes, cooling the mixture using an ice water bath. This mixture is transferred to a 2000 mL bottle.

The bottle is closed and then placed in an oven at room temperature. The oven is heated to 40 ° C with a ramp of 3 ° C per minute. The API matures for 24 hours at 40 ° C.

Then the gel is heated to 80 ° C and maintained at this temperature for 48 hours. After this period, the bottle is suddenly cooled by quenching in an ice water bath. This suspension of zeolite Y in its reaction medium is called suspension S1. The isothermal analysis of nitrogen adsorption of part of the zeolite which has been washed and calcined at 500 ° C. for 4 hours gives a microporous volume of 0.33 cc / g and a surface

BET (Sbet) of 860 m ² / g. The X-ray diffractogram (XRD) (FIG. 1) of a part of the zeolite which has been washed and calcined at 500 ° C. for 4 hours confirms the obtaining of a pure Y zeolite.

The size of the crystallite agglomerates determined by laser granulometry of the zeolite suspension in its reaction medium is centered on 230 nm.

2- Precipitation of the alumina precursor in the presence of the zeolite Y in its reaction medium

1000 mL of distilled water are introduced into a perfectly stirred 5 liter reactor at a temperature of 70 ° C. The suspension S1 of zeolite Y in its reaction medium (2 L), and the acid aluminum salt (1058 mL solution of AI (NO ₃ ) ₃ at 102 g / L in AI ₂ O ₃ ) are introduced simultaneously and continuously for 30 min with pH regulation at 9.7. The agitation is 350 rpm throughout the synthesis.

All of the precursors are brought into contact at a temperature of 70 ° C. The final concentration of targeted alumina is 46 g / L and the percentage of zeolite in the final product after calcination is targeted at 56%. The suspension obtained is then filtered and washed 3 times with 5 L of distilled water at 70 ° C.

The cake thus obtained is dried for 12 hours in an oven at 120 ° C and the dried product is ground. The powder will hereinafter be called powder A1.

3- Powder shaping

The powder A1 is shaped by kneading-extrusion according to the following protocol: 27.3 g of powder A1 is introduced into a mixing tool by kneading and whose arm rotation speed is 30 revolutions per minute, as well as simultaneously 20.6 g of distilled water and 0.8 g of nitric acid HNO ₃ at 69% m / m. Leave to mix for 60 min. The paste thus obtained is discharged and introduced into a piston extruder and the outlet of the extruder is equipped with a die of cylindrical shape and diameter 2 mm.

The extrudates thus obtained are dried in an oven for 1 night at 80 ° C, then they are calcined in a muffle oven at 600 ° C for 4 hours. Extruded B1 are thus obtained. X-ray diffraction analysis reveals that the diffraction peaks obtained are characteristic of gamma alumina and of zeolite Y (Figure 2). The analyzes by mercury porosimetry and isothermal nitrogen adsorption / desorption give the texture (Table 1).

Figure 3 is the SEM image of the porous composite material obtained in the example above at the end of the shaping step e). It is noted that the crystals of zeolite Y, (noted A) are well dispersed within the gamma alumina (noted B), and that there is no aggregation phenomenon. Indeed, the size of the zeolite crystallite agglomerates measured is 200-250 nm in good agreement with the value determined by laser particle size of the zeolite suspension in its reaction medium (centered on 230 nm). The zeolite crystals therefore have dimensions of the order of dimensions of the zeolite crystals obtained in step 1) of synthesis of the zeolite.

In addition, the microporous volume of the extrudates is in good agreement with the percentage of zeolite present in the extrudates. This characteristic confirms that the microporous volume of the zeolite crystals contained in the porous composite material corresponds to the microporous volume of the zeolite crystals obtained at the end of step 1 and therefore that the properties of the zeolite crystals, in particular their texture, are preserved while along the synthesis of the porous composite material.

Example 2: shaping by adding zeolite powder to the precipitation of the alumina precursor (non-compliant)

The procedure used for the synthesis of zeolite Y is identical to that of Example 1. The size of the crystallite agglomerates determined by laser particle size distribution of the zeolite suspension in its reaction medium is centered on 220 nm.

After synthesis, the zeolite is filtered and washed several times with distilled water until pH = 8. Then it is dried for 12 hours at 80 ° C and calcined for 2 hours at 500 ° C. The powder will hereinafter be called powder P2.

The analysis by laser granulometry of the zeolite P2 powder after filtration, washing, drying and calcination has an aggregate size centered on 20 microns. SEM analysis of the powder confirms this value (Figure 4).

700 ml of distilled water and 200 g of anhydrous zeolite Y powder P2 are introduced into a perfectly stirred reactor. The precipitation takes place at a temperature of 70 ° C and a pH of 9.7. The reagents (basic aluminum salt [AlOONa] and acid [AI ₂ (SO ₄ ) ₃ ]) are added continuously for 30 min with pH regulation at 9. The concentrations of the aluminum precursors used are the following: AI ₂ (SO ₄ ) = at 102g / L in AI ₂ O ₃ and AlOONa at 155g / L in AI ₂ O ₃ . The agitation is 350 rpm throughout the synthesis.

All of the precursors are brought into contact at a temperature of 70 ° C. The final concentration of alumina targeted is 50 g / L. The suspension obtained is then filtered by displacement of water on a sintered Buchner type tool and the solid obtained is washed 3 times with 3.5L of distilled water at 70 ° C.

The cake thus obtained is dried for 12 hours in an oven at 120 ° C and the dried product is ground. The powder will hereinafter be called powder A2.

The A2 powder is shaped by kneading-extrusion according to the following protocol: 27.3 g of A2 powder is introduced into a mixing tool by kneading and the arm rotation speed of 30 revolutions per minute, then simultaneously 20 , 6 g of distilled water and 0.8 g of nitric acid HNO ₃ at 69% m / m. Leave to mix for 60 min. The paste thus obtained is discharged and introduced into a piston extruder and the outlet of the extruder is equipped with a track die of cylindrical shape and diameter 2 mm.

The extrudates thus obtained are dried in an oven for 12 hours at 80 ° C, then they are calcined in a muffle oven at 600 ° C for 4 hours. The extruded B6 are thus obtained. X-ray diffraction analysis reveals that the diffraction peaks obtained are characteristic of gamma alumina and of zeolite Y. Analyzes by mercury porosimetry and isothermal nitrogen adsorption / desorption give the texture (Table 1 ).

The texture of the extrudates calcined in an oven at 600 ° C. for 4 hours is given in Table 1

FIG. 4 is the SEM image of the agglomerates obtained in the example above at the end of the drying step. It can be seen that the zeolite crystals Y have much larger dimensions (20 μm) compared to the dimensions of the zeolite crystals obtained in the zeolite synthesis step (220 nm).

FIG. 5 is the SEM image of the agglomerates obtained in the example above at the end of the step after the shaping step. It is noted that the crystals of zeolite Y (noted A) within the gamma alumina matrix (noted B) have dimensions of the order of 10-25 μm corresponding to the dimensions observed after drying (FIG. 4). The extrusion kneading operation therefore does not make it possible to find the initial size of the zeolite agglomerates in its reaction medium, nor to homogeneously disperse the zeolite crystals within the aluminum matrix.

Example 3: preparation of zeolite-gamma alumina extrudates (according to the invention).

1- Synthesis of the ZSM-5 zeolite

a) preparation of ZSM-5 germs.

The molar ratio between the various reactants is: 4.5 (TPA) ₂ O / 25 SiO _2/430 H ₂ O with TPA = tetrapropylammonium hydroxide, the source of SiO ₂ is tetraethylorthosilicate. After mixing, the solution is left to hydrolyze TPA and TEOS at room temperature for 14 hours and then it is treated in a closed bottle at 90 ° C for 24 hours. The product is recovered and washed by successive centrifugations with water and then dried at 100 ° C for 12 hours. The powder æra hereinafter called powder P3.

b) synthesis of the zeolite.

The composition of the synthesis gel is: 7.5 Na ₂ O / 0.88 Al ₂ O _3/25 SiO _2/1200 H ₂ O and 3% germ (powder P3) relative to the amount of silica are added as . The source of silica and sodium is a solution of sodium silicate and the source of aluminum is aluminum sulfate. Crystallization is carried out at 170 ° C for 24 hours. This suspension of ZSM-5 zeolite in its reaction medium is called suspension S3. The suspension of zeolite crystals in its reaction medium is then used as basic source of zeolite for the precipitation of the alumina precursor. Isothermal analysis of nitrogen adsorption of part of the suspension S3 washed and calcined at 500 ° C for 4 hours gives a microporous volume of 0.13 cc / g. The X-ray diffractogram (FIG. 6) of a part of the zeolite which has been washed and calcined at 500 ° C. for 4 hours confirms the obtaining of a pure ZSM-5 zeolite.

Analysis by laser granulometry of the zeolite crystals in its reaction medium (suspension S3) shows an aggregate size centered on 500 nm.

2- Precipitation of the alumina precursor in the presence of the zeolite ZSM-5 in its reaction medium.

2.16 liters of suspension S3 of zeolite ZSM-5 are introduced into its reaction medium in a perfectly stirred 3.5 liter batch reactor at a temperature of 70 ° C. The addition of the solution at 70 ° C. of acid precursor (245 mL A (NO ₃ ) ₃ to 102 g / L in AI ₂ O ₃ ) w is carried out continuously for 2 minutes until a pH of 9.5 and the suspension is kept under stirring at 70 ° C for another 30 minutes. The agitaticn is 350 rotations per minute (rpm) throughout the synthesis. The final concentration of alumina targeted is 10 g / L. The suspension obtained is then filtered through a sintered Buchner and the cake obtained, composed of a mixture of alumina-zeolite precursor, is washed 5 times with 3.5 liters of distilled water at 70 ° C.

The cake thus obtained is dried for 12 hours in an oven at 120 ° C and the dried product is ground. This product is called A3 powder.

3- Powder shaping

The powder A3 composed of both an alumina precursor and a zeolite is shaped by kneading-extrusion according to the following protocol: in a kneading mixing tool, the rotation speed of the arms is 30 revolutions per minute, 27.3 g of A3 powder and 0.2 g of METHOCEL ™ are introduced, then simultaneously 20.6 g of distilled water and 0.4 g of nitric acid HNO ₃ at 69% m / m. The mixture is kneaded for 60 minutes, then 1.1 g of distilled water and 0.15 g of ammonia at 30% m / m are simultaneously introduced. The mixture is kneaded for 20 min.

The dough thus obtained is discharged and introduced into a piston extruder and the exit of the extruder is equipped with a track die of cylindrical shape and diameter 2 mm.

The extrudates thus obtained are dried in an oven for 12 hours at 80 ° C, then calcined in a muffle oven at 600 ° C for 4 hours. They are called extruded B3. The X-ray diffraction analysis reveals that the diffraction peaks obtained are characteristic of gamma alumina and of the zeolite ZSM-5 (Figure 7). The extrudates contain after calcination 89% by mass of zeolite ZSM-5 and 11% of gamma alumina.

The texture of the extrudates calcined in an oven at 600 ° C. for 4 hours is given in Table 1. The characterization by Scanning Electron Microscopy of an extruded B3 shows a very good dispersion of the zeolite in the alumina matrix. The size of the zeolite crystallite agglomerates is 450-550 nm, in good agreement with the value determined by laser granulometry of the zeolite suspension in its reaction medium (centered on 500 nm). The zeolite crystals therefore have dimensions of the order of dimensions of the zeolite crystals obtained in the step of synthesizing the zeolite.

In addition, the microporous volume of the extrudates is in good agreement with the percentage of zeolite present in the extrudates. This characteristic confirms that the microporous volume of the zeolite crystals contained in the porous composite material corresponds to the microporous volume of the zeolite crystals obtained at the end of step 1 and therefore that the properties of the zeolite crystals, in particular their texture, are preserved while along the synthesis of the porous composite material.

Example 4 Preparation of ZSM-5 zeolite-gamma alumina extrudates (according to the invention).

1- Synthesis of the ZSM-5 zeolite

The procedure used for the synthesis of the ZSM-5 zeolite is identical to that of Example 3. This suspension of ZSM-5 zeolite in its reaction medium is called suspension S4.

Analysis by laser granulometry of the zeolite crystals in its reaction medium (suspension S4) shows an aggregate size centered on 520 nm.

2- Precipitation of the alumina precursor in the presence of the zeolite ZSM-5 in its reaction medium.

2.16 liters of suspension S4 of zeolite ZSM-5 are introduced into its reaction medium in a perfectly stirred 6-liter reactor at a temperature of 70 ° C. The acid precursor (1960 mL solution of AI (NO ₃ ) ₃ at 102 g / L in AI ₂ O ₃ ) and concentrated sodium hydroxide solution (420g NaOH in 1L water) are added simultaneously at 70 ° C. continuous for 2 minutes until a pH of 9.5. The suspension is stirred at 70 ° C for 30 minutes. The agitation is 350 rpm throughout the synthesis. The final alumina concentration is 33 g / L. The suspension obtained is then filtered through a sintered Buchner and the mixture of alumina-zeolite precursor obtained is washed 5 times with 6 liters of distilled water at 70 ° C.

The cake thus obtained is dried for 12 hours in an oven at 120 ° C and the dried product is ground. This product is called A4 powder.

3- Powder shaping

The A4 powder composed of both the alumina precursor and the zeolite ZSM-5 is shaped by kneading-extrusion according to the following protocol: in a mixing tool by kneading, the rotation speed of the arms is 30 revolutions per minute, 27.3 g of A4 powder are introduced, then 20.6 g of distilled water and 0.8 g of nitric acid HNO ₃ at 69% m / m. The mixture is left to mix for 60 min, then 1.1 g of distilled water and 0.3 g of ammonia at 30% m / m are introduced. The whole is left to knead for 20 min.

The dough thus obtained is discharged and introduced into a piston extruder and the exit of the extruder is equipped with a track die of cylindrical shape and diameter 2 mm.

The extrudates thus obtained are dried in a study for 1 night at 80 ° C, then they are calcined in a muffle furnace at 600 ° C for 4 hours. The B4 extrudates thus obtained contain, after calcination, 50% by mass of ZSM-5 zeolite and 50% of gamma alumina.

The X-ray diffraction analysis reveals that the diffraction peaks obtained are characteristic of gamma alumina and of the zeolite ZSM-5 (Figure 8). The analyzes by mercury porosimetry and isothermal nitrogen adsorption / desorption give the texture (Table 1).

The texture of the extrudates calcined in an oven at 600 ° C. for 4 hours is given in the

Table 1. The characterization by Scanning Electron Microscopy of an extruded B4 shows a very good dispersion of the zeolite in the alumina matrix. The size of the zeolite crystallite agglomerates is 470-560 nm in good agreement with the value determined by laser granulometry of the zeolite suspension in its reaction medium (centered on 520 nm).

In addition, the microporous volume of the extrudates is in good agreement with the percentage of zeolite present in the extrudates. This characteristic confirms that the microporous volume of the zeolite crystals contained in the porous composite material corresponds to the microporous volume of the zeolite crystals obtained at the end of step 1 and therefore that the properties of the zeolite crystals, in particular their texture, are preserved while along the synthesis of the porous composite material.

Example 5: preparation of zeolite-gamma alumina extrudates (according to the invention).

1- Synthesis of the ZSM-5 zeolite

The procedure used for the synthesis of the ZSM-5 zeolite is identical to that of Example 3. This suspension of ZSM-5 zeolite in its reaction medium is called suspension S5.

Analysis by laser granulometry of the zeolite crystals in its reaction medium (suspension S5) shows an aggregate size centered on 470 nm.

2- Precipitation of the alumina precursor in the presence of the zeolite ZSM-5 in its reaction medium.

2.16 liters of suspension S5 of zeolite ZSM-5 are introduced into its reaction medium in a perfectly stirred 5 liter batch reactor at a temperature of 70 ° C. The addition at 70 ° C of the acid precursor (245 mL solution of AI (ND ₃ ) ₃ at 102 g / L in AI ₂ O ₃ ) is carried out continuously for 2 minutes until a pH of 9.5. The basic aluminum precursor (845 mL AlOONa solution 155 g / L as AI ₂ O ₃ ) and the aluminum acid precursor (441 mL AI solution (NO ₃ ) ₃ at 102 g / L as AI ₂ O ₃ ) is carried out simultaneously and continuously for 30 min with pH regulation at 9.7 to have a final zeolite / alumina mass ratio equal to 1. The stirring speed is 350 rotations per minute (rpm).

All of the precursors are brought into contact at a temperature of 70 ° C. The final alumina concentration is 54 g / L. The suspension obtained is then filtered by displacement of water on a sintered Buchner type tool and the solid (zeolite + alumina precursor) obtained is washed 3 times with 5 L of distilled water at 70 ° C.

The cake thus obtained is dried for 12 hours in an oven at 120 ° C and the dried product is ground. The powder will hereinafter be called powder A5.

3- Powder shaping

The powder A5 is shaped by kneading-extrusion according to the following protocol: in a mixing tool by kneading and whose arm rotation speed is 25 revolutions per minute, 27.3 g of powder A5 is introduced then 20, 6 g of distilled water and 0.8 g of nitric acid HNO ₃ at 69% m / m. The mixture is left to mix for 60 minutes, then 1.1 g of distilled water and 0.3 g of ammonia at 30% m / m are introduced. The mixture is kneaded for 20 min.

The dough thus obtained is discharged and introduced into a piston extruder and the exit of the extruder is equipped with a track die of cylindrical shape and diameter 2 mm.

The extrudates thus obtained are dried in a study overnight at 80 ° C, then they are calcined in a muffle furnace at 600 ° C for 4 hours. The B5 extrudates are thus obtained and contain 50% by mass of ZSM-5 zeolite and 50% of gamma alumina. The X-ray diffraction analysis reveals that the diffraction peaks obtained are characteristic of gamma alumina and of the zeolite ZSM-5 (Figure 9). The analyzes by mercury porosimetry and isothermal nitrogen adsorption / desorption give the texture (Table 1).

The texture of the extrudates calcined in an oven at 600 ° C. for 4 hours is given in Table 1.

The characterization by Scanning Electron Microscopy of an extruded B5 shows a very good dispersion of the zeolite in the alumina matrix. The size of the zeolite crystallite agglomerates is 460-500 nm in good agreement with the value determined by laser granulometry of the zeolite suspension in its reaction medium (centered on 470 nm).

In addition, the microporous volume of the extrudates is in good agreement with the percentage of zeolite present in the extrudates. This characteristic confirms that the microporous volume of the zeolite crystals contained in the porous composite material corresponds to the microporous volume of the zeolite crystals obtained at the end of step 1 and therefore that the properties of the zeolite crystals, in particular their texture, are preserved while along the synthesis of the porous composite material.

Example 6: Preparation of zeolite-gamma alumina extrudates (according to the invention).

1- Synthesis of the ZSM-5 zeolite

The procedure used for the synthesis of the ZSM-5 zeolite is identical to that of Example 3. This suspension of ZSM-5 zeolite in its reaction medium is called suspension S6.

Analysis by laser granulometry of the zeolite crystals in its reaction medium (suspension S6) shows an aggregate size centered on 490 nm.

2- Precipitation of the alumina precursor in the presence of the zeolite ZSM-5 in its reaction medium.

1000 ml of distilled water are introduced into a perfectly stirred 5 liter batch reactor at a temperature of 70 ° C. The suspension S6 obtained in the previous step (2.16 L), the basic aluminum precursor (845 mL AlOONa solution at 155 g / L as AI ₂ O ₃ ) and the aluminum acid precursor (686 mL solution of AI (NO ₃ ) ₃ at 102 g / L in AI ₂ O ₃ ) are introduced simultaneously and continuously for 30 min up to a pH of 9.7. The agitation is 350 rpm.

All of the precursors are brought into contact at a temperature of 70 ° C. The final alumina concentration is 54 g / L and the percentage of zeolite in the final product after calcination is 40%. The suspension obtained is then filtered through a sintered Buchner and the solid (zeolite + alumina precursor) obtained is washed 3 times with 3.5 L of distilled water at 70 ° C.

The cake thus obtained is dried for 24 hours in an oven at 120 ° C and the dried product is ground. The powder will hereinafter be called powder A6.

3- Powder shaping

The powder A6 is shaped by kneading-extrusion according to the following protocol: in a mixing tool by kneading, and whose rotation speed of the arms is 30 rotations per minute (rpm), 27.3 g of powder are introduced A6 then 20.6 g of distilled water and 0.8 g of nitric acid HNO ₃ at 69% m / m. The mixture is kneaded for 60 min.

The dough thus obtained is discharged and introduced into a piston extruder and the exit of the extruder is equipped with a track die of cylindrical shape and diameter 2 mm.

The extrudates thus obtained are dried in a study overnight at 80 ° C, then they are calcined in a muffle furnace at 600 ° C for 4 hours. The B6 extrudates are thus obtained and contain 50% by mass of ZSM-5 zeolite and 50% of gamma alumina. The X-ray diffraction analysis reveals that the diffraction peaks obtained are characteristic of gamma alumina and of the zeolite ZSM-5 (Figure 10). The analyzes by mercury porosimetry and isothermal nitrogen adsorption / desorption give the texture (Table 1).

The texture of the extrudates calcined in an oven at 600 ° C. for 4 hours is given in Table 1. The characterization by Scanning Electron Microscopy of an extruded B6 shows a very good dispersion of the zeolite in the alumina matrix. The size of the zeolite crystallite agglomerates is 460-520 nm, in good agreement with the value determined by laser granulometry of the zeolite suspension in its reaction medium (centered on 490 nm).

In addition, the microporous volume of the extrudates is in good agreement with the percentage of zeolite present in the extrudates. This characteristic confirms that the microporous volume of the zeolite crystals contained in the porous composite material corresponds to the microporous volume of the zeolite crystals obtained at the end of step 1 and therefore that the properties of the zeolite crystals, in particular their texture, are preserved. all along the synthesis of the porous composite material.

Table 1: Porous texture of the gamma-zeolite alumina extrudates obtained in Examples 1 to 6.

extruded name B1 B2 B3 B4 B5 B6 BET area (m ² / g) 600 580 160 380 360 360 Total pore volume Hg (cm ³ / g) 1.15 1.20 1.22 1.07 1.05 1.00 Mesoporous volume Hg (cm ³ / g) 0.29 0.27 0.31 0.65 0.60 0.54 Microporous volume (cm ³ / g) 0.182 0.176 0.116 0.066 0.065 0.063 Mesoporous Dp at dV / dDp max (nm) 9.1 8.7 30.2 11.3 10.7 12.2

Claims (14)

1. Process for the preparation of a porous composite material comprising at least one zeolite and at least one alumina precursor, said process comprising at least the following steps: 5 a) a step for obtaining zeolite crystals in suspension in the synthetic reaction medium, b) at least one step of precipitating at least one alumina precursor in the suspension obtained at the end of step a), by bringing at least one acidic aluminum precursor into contact. îo 2. Method according to claim 1 wherein step a) comprises a step of reacting in an aqueous mixture, at least one source of at least one oxide XO ₂ , at least one source of at least one oxide Y2O3, of at least one basic source of at least one alkali and / or alkaline-earth metal M of valence n, and / or at least one organic species R comprising one or more 15 quaternary nitrogen atoms or one phosphorus atom, in which X represents at least one tetravalent element chosen from silicon, germanium, titanium and the mixture of at least two of these tetravalent elements Y represents at least one trivalent element, chosen from aluminum, boron, 20 iron, indium and gallium M is at least one alkali metal and / or one alkaline earth metal of valence n, chosen from lithium, sodium, potassium, calcium, magnesium and the mixture of at least two of these metals R is chosen from tetrapropylammonium bromide, 25 tetrapropylammonium, 18-crown-6 ether, hexamethonium dibromide, tetraethylammonium hydroxide, ethylene diamine, 2,6dimethylpiperidine. 3. Method according to claim 2 in which X is silicon, Y is aluminum, and M is sodium. 4. Method according to one of claims 1 to 3 in which seeds comprising zeolite crystals are added during step a). 5. Method according to one of claims 1 to 4 wherein, step a) comprises a hydrothermal treatment of the mixture obtained, carried out at an autogenous reaction pressure at a temperature between 40 ° C and 200 ° C, and for îo a duration of between 2 hours and 21 days. 6. Method according to one of claims 1 to 5 wherein the acidic aluminum precursor used in step b) of precipitation, is chosen from aluminum sulfate, aluminum chloride, aluminum nitrate . 7. Method according to one of claims 1 to 6 wherein step b) of 15 precipitation is carried out in the presence of at least one additional basic precursor, chosen from sodium aluminate, potassium aluminate, ammonia, sodium hydroxide and potassium hydroxide. 8. The method of claim 7 wherein the basic precursor and / or the additional basic precursor is added simultaneously to the precursor 20 acid. 9. Method according to one of claims 1 to 8 wherein a second precipitation step b ') is carried out, after the first step b), by adding to the suspension obtained in step b) at least at least one acid precursor chosen from aluminum sulphate, aluminum chloride, nitrate 25 of aluminum and optionally an additional basic precursor chosen from sodium aluminate, potassium aluminate, ammonia, sodium hydroxide and sodium hydroxide. 10. Method according to one of claims 1 to 9 wherein step b) or b ’) of precipitation is carried out at a pH of the reaction medium between 7 and 12 and for a period between 2 minutes and 50 minutes. 11. Method according to one of claims 1 to 10 wherein a step of 5 ripening is carried out after one of steps b or b ') of precipitation, said ripening step being carried out at a temperature between 65 and 150 ° C, and for a period of time between 40 minutes and 5 hours . 12. Method according to one of claims 1 to 11 comprising a step c) of filtration and washing of the suspension obtained at the end of step b) or b ') of precipitation, said washing step being carried out with an aqueous solution at a temperature between 20 and 70 ° C. 13. The method of claim 12 comprising a step d) of drying the cake obtained at the end of step c) of filtration and washing, carried out at a temperature between 80 and 120 ° C. 14. The method according to claim 13, in which a step e) of shaping the powder obtained at the end of step d) of drying is carried out by kneading, extrusion, by tableting, by the method of coagulation drop (oil-drop), by atomization, by granulation on the turntable. 15. The method of claim 14 wherein a step f) of calcination is 20 carried out after stage d) of drying or after stage e) of shaping, said calcination stage being carried out at a temperature between 500 and 1000 ° C., for a period of between 2 and 10 h. 1/5