PROCESS FOR PREPARING A ZEOLITHIC MATERIAL WITH A HIGH KL ZEOLITE CONTENT AND HIGH MECHANICAL STRENGTH

Abstract

The present invention relates to a method for preparing a microporous material shaped into extrudates, tablets or beads having good mechanical resistance to crushing and containing at least 90% by mass of KL zeolite (structural type LTL). This method comprises a step of shaping a KL zeolite with at least one zeolithizable binder and at least one zeolitization step, in the presence of potassium hydroxide at one and / or the other of the steps, in order to obtain a material shaped into extrudates, tablets or beads, containing at least 90% by mass of KL zeolite and good mechanical resistance to crushing. Figure 4 to be published

Description

Title of the invention: PROCESS FOR PREPARING A ZEOLITHIC MATERIAL WITH A HIGH KL ZEOLITE CONTENT AND HIGH MECHANICAL STRENGTH Technical field

[0001] The present invention relates to a method for preparing a microporous material shaped in the form of extrudates, tablets or beads having good mechanical resistance to crushing, and containing at least 90% by mass of KL zeolite (structural type LTL). This method comprises a step of shaping this zeolite in powder form with at least one zeolithizable binder and at least one zeolitization step, in order to obtain a shaped material, containing at least 90% by mass of KL zeolite and good mechanical resistance to crushing. Prior art

[0002] Zeolites are crystalline aluminosilicate materials with organized microporosity formed by the three-dimensional arrangement of SiO44 and A1O45 tetrahedra, thus providing a wide diversity of structures. The International Zeolite Association (IZA) has classified zeolites according to their structures (structural types). Zeolites are widely used in industry for adsorption, separation, catalysis and ion exchange. To be used in industrial processes, zeolites are shaped to obtain objects larger than zeolite crystals, and thus facilitate their handling, but also facilitate the passage of the charge in the reactors. KL zeolite is a zeolite of the LTL structural type containing a one-dimensional microporous system with pore openings of 12 T atoms (T being silicon or aluminum).The charge compensating cation of the structure is K+.

[0003] Patent US4830732 presents a method for obtaining a shaped material containing a KL zeolite. The method consists of mixing a KL zeolite with a silica or a pseudo-boehmite and then shaping the mixture by kneading-extrusion. Aluminum nitrate is added to increase the mechanical strength of the extrudates. The percentage of KL zeolite relative to the total mass of KL zeolite and silica or pseudo-boehmite is 80%. The patent does not present any data in the examples on the mechanical strength of the extrudates obtained.

[0004] Patent US5354933 presents a method for obtaining a shaped material containing a KL zeolite. The method consists of mixing a KL zeolite with a silica, then shaping the mixture by kneading-extrusion. The percentage of KL zeolite relative to the total mass of KL zeolite and silica is 83%. The patent does not present any data on the mechanical strength of the extrudates obtained.

[0005] Patent US5980731 presents a material shaped in the form of extrudates containing an MgKL zeolite and alumina. The percentage of MgKL zeolite relative to the total mass of MgKL zeolite and alumina is 70%. The patent does not present any data on the mechanical strength of the extrudates obtained.

[0006] Patent US6207042 presents a method for obtaining a shaped material containing a KL zeolite. The method consists of mixing a KL zeolite with a silica and methocel, then shaping the mixture by kneading-extrusion. The percentage of KL zeolite relative to the total mass of KL zeolite and silica is 83%. The patent does not present any data on the mechanical strength of the extrudates obtained.

[0007] Patent US6358400 presents a material shaped in the form of extrudates containing a SnKL zeolite and silica. The percentage of SnKL zeolite relative to the total mass of SnKL zeolite and silica is 85%. The patent does not present any data on the mechanical strength of the extrudates obtained.

[0008] Patent US8263518 presents a material shaped in the form of extrudates containing a KL zeolite and silica. The percentage of KL zeolite relative to the total mass of KL zeolite and silica is 83%. The patent does not present any data on the microporous volume of the extrudates obtained. The mechanical resistance of the extrudates obtained is greater than 3 Ibf / mm (1.3 daN / mm).

[0009] The methods of the prior art show that it is very difficult to shape a mixture containing a very high content of KL zeolite and to obtain a shaped object having good mechanical resistance.

[0010] Surprisingly, the Applicant has discovered that the shaping of a zeolitic material in the form of extrudates, tablets, or beads starting from KL zeolite mixed with at least one zeolithizable binder, followed by a zeolitization step, in the presence of potassium hydroxide at one and / or other of the steps of the process, leads to a material containing at least 90% by mass of KL zeolite, while having good mechanical strength. Summary of the invention

[0011] The invention relates to a process for preparing a zeolitic microporous material shaped in the form of extrudates, tablets or beads having a mechanical crushing strength greater than or equal to 0.7 daN / mm and containing at least 90% by mass of KL zeolite of LTL structural type, comprising:

[0012] i) a step of shaping a KL zeolite powder, mixed with at least one zeolithizable binder, optionally in the presence of potassium hydroxide to obtain extrudates, tablets or balls of partially zeolitic material;

[0013] ii) at least one step of zeolitization of said partially zeolitic material shaped in step i) by contacting with water or with an aqueous solution of potassium hydroxide in vapor or liquid form at a temperature of between 95 and 200°C for a period of between 5 and 72 hours, washing, then drying in order to obtain a microporous zeolitic material in the form of extrudates, tablets or balls containing at least 90% by mass of KL zeolite, and having a mechanical crushing strength greater than or equal to 0.7 daN / mm,

[0014] the potassium hydroxide being introduced in step i) and / or in step ii).

[0015] Said at least one zeolithizable binder may be chosen from kaolin, metakaolin or any other zeolithizable clay, or mixtures of silica and alumina such as colloidal silica, pyrogenic silicas, sodium silicate, sodium aluminate, boehmites or aluminum hydroxide, alone or as a mixture.

[0016] Shaping can be done by extrusion, pelletizing, agglomeration or spheronization.

[0017] Step i) may comprise gentle drying of the shaped extrudates, beads or tablets at a temperature of between 60 and 95°C, preferably between 75 and 90°C for a period of between 1 and 24 hours.

[0018] Said drying may be followed by calcination of the dried extrudates, balls or tablets at a temperature of between 300 and 550°C for a period of between 2 and 8 hours.

[0019] In one embodiment, the dried and optionally calcined extrudates, beads or tablets may be impregnated with a potassium hydroxide solution before step ii) of zeolitization.

[0020] Said zeolitization step ii) can be carried out by heat treatment in the presence of water or a potassium hydroxide solution under autogenous pressure in a closed reactor.

[0021] In a first variant, said shaped partially zeolitic material can be brought into contact with water by immersion in water or aqueous potassium hydroxide solution in liquid form.

[0022] In a second variant, said shaped partially zeolitic material can be brought into contact with water or the aqueous solution of potassium hydroxide in vapor form.

[0023] The zeolitic material obtained after the zeolitization of step ii) can be washed several times with water to obtain a final pH in the washing waters of between 7 and 8, then dried at a temperature of between 80 and 130°C, preferably between 90 and 120°C for 1 to 24 hours, preferably between 2 and 12 hours.

[0024] The preparation process according to the invention may comprise a step iii) of cal cation of the extradits, balls, tablets of zeolitic microporous material obtained in step ii) at a temperature of between 300 and 550°C for a period of between 2 and 8 hours, after the zeolitization step(s) ii).

[0025] The zeolithizable binder may comprise a source of alumina which is aluminum hydroxide, and a source of silica which is colloidal silica.

[0026] The zeolithizable binder may comprise kaolin or meta kaolin.

[0027] The quantity of potassium hydroxide optionally introduced in step i) is advantageously chosen to obtain a molar ratio between the silica of the zeolithizable binder considered in its SiO2 form and the potassium considered in its K2O form of between 3 and 5, limits included and the quantity of potassium hydroxide optionally introduced in step ii) of zeolitization is advantageously chosen to obtain a molar ratio between the silica source of the zeolithizable binder considered in its SiO2 oxide form and the potassium hydroxide considered in its K2O oxide form of between 0.5 and 5, limits included.

[0028] Potassium hydroxide can be introduced in both steps i) and ii) and the total amount of potassium hydroxide introduced in steps i) and ii) is chosen to obtain a molar ratio between the silica source of the zeolithizable binder considered in its oxide form SiO2 and the potassium hydroxide considered in its oxide form K2O of between 3 and 5, limits included.

[0029] The invention also relates to the use of the zeolitic microporous material obtained according to any one of the variants of the process according to the invention as a catalyst support, adsorbent or separation agent. LIST OF FIGURES

[0030] Other characteristics and advantages of the method according to the invention will appear on reading the following description of non-limiting examples of embodiments, with reference to the appended figures described below. [Fig 1]

[0031] [Fig.l] represents the X-ray diffraction (XRD) diagram of pure KL zeolite (reference sample) obtained according to Example 1. [Fig 2]

[0032] [Fig.2] represents the X-ray diffraction (XRD) diagram of the zeolitic microporous material obtained according to example 2. [Fig 3]

[0033] [Fig. 3] represents the X-ray diffraction (XRD) diagram of the zeolitic microporous material obtained according to example 3. [Fig 4]

[0034] [Fig.4] represents the X-ray diffraction (XRD) pattern of the material microporous zeolite obtained according to example 4. [Fig 5]

[0035] [Fig.5] represents the X-ray diffraction (XRD) diagram of the zeolitic microporous material obtained according to example 5. [Fig 6]

[0036] [Fig.6] represents the X-ray diffraction (XRD) diagram of the zeolitic microporous material obtained according to Example 6. Description of the embodiments

[0037] According to the invention, the Si / Al molar ratio defines the molar ratio between the molar quantity of silicon element, denoted Si, and the molar quantity of aluminum element, denoted Al, of the microporous aluminosilicate KL zeolite of LTL structural type. The Si / Al ratios are calculated from the molar quantities of the silicon element Si and the aluminum element Al present in the microporous zeolitic material considered, said molar quantities being determined by the X-ray Fluorescence spectrometry method.

[0038] According to the present invention, the expression "between ... and ..." means that the limit values of the interval are included in the range of values described. If this were not the case and the limit values were not included in the range described, such precision will be provided by the present invention.

[0039] According to the present invention, the expression "under autogenous pressure" means the pressure generated in a closed reactor and subjected to temperatures above 25°C by the simple evaporation of the water present in this reactor.

[0040] According to the present invention, the expression "zeolitizable binder" means any source of silica and alumina which is easily transformed into KL zeolite in the presence of potassium hydroxide.

[0041] According to the present invention the expression "zeolitization" means the process during which the source of silica and alumina is transformed into KL zeolite in the presence of potassium hydroxide.

[0042] According to the present invention, the “loss on ignition” (LAI) is the percentage loss of mass of a solid after its calcination at 1000°C for 1 hour.

[0043] Furthermore, in the following, particular and / or preferred embodiments of the invention may be described. They may be implemented separately or combined with each other, without limitation of combination when this is technically feasible.

[0044] The present invention relates to a method for preparing a shaped zeolitic microporous material (MEF) in the form of extrudates, tablets, or beads having good mechanical resistance to crushing and high content of KL zeolite, i.e. containing at least 90% by mass of KL zeolite (structural type LTL). Said process comprises at least:

[0045] -a step of shaping a mixture of a KL zeolite with at least one zeolithizable binder to obtain extrudates, tablets or beads;

[0046] -and at least one zeolitization step, in order to obtain a material containing at least 90% by mass of KL zeolite having good mechanical resistance to crushing, one and / or the other of the steps being carried out in the presence of potassium hydroxide.

[0047] If necessary, the zeolitization step can be repeated one or more times in order to reach the required percentage of KL zeolite.

[0048] The shaping can be done by any method known to those skilled in the art, such as for example by extrusion, in particular kneading-extrusion if necessary, pelletizing, agglomeration or spheronization.

[0049] A material as obtained by the process according to the present invention containing more than 90% by mass of KL zeolite and having a high mechanical resistance, in particular greater than or equal to 0.7 daN / mm, can then advantageously be used as an adsorbent, catalyst support or separation agent.

[0050] More particularly, the invention relates to a process for preparing a zeolitic microporous material shaped in the form of extrudates, tablets or beads, having a mechanical crushing strength greater than or equal to 0.7 daN / mm, and containing at least 90% by mass of KL zeolite of LTL structural type, from KL zeolite and in the presence of potassium hydroxide at one and / or other of the stages, comprising:

[0051] i) a step of shaping said KL zeolite in a mixture with at least one zeolitizable binder and optionally potassium hydroxide to obtain a partially zeolitic material shaped into extrudates, tablets or beads. The content of KL zeolite in the shaped mixture is advantageously at least 60%, preferably between 60 and 80% by weight relative to the dry matter.

[0052] ii) at least one step of zeolitization of said partially zeolitic material shaped in step i) by contacting with water in vapor or liquid form or with a potassium hydroxide solution in vapor or liquid form at a temperature between 95 and 200°C, for a period of 5 to 72 hours, followed by washing, then drying in order to obtain a microporous zeolitic material in the form of extrudates, tablets or beads containing at least 90% by mass of KL zeolite, having a mechanical crushing strength greater than or equal to 0.7 daN / mm.

[0053] The zeolithizable binder may be chosen from kaolin, metakaolin or any other zeolithizable clay known to those skilled in the art, or mixtures of silica and alumina such as colloidal silica, pyrogenic silicas, sodium silicate, sodium aluminate, boehmites or aluminum hydroxide, preferably the zeolithizable binder is introduced at a content of between 10 and 40% relative to the total mass of anhydrous material obtained at the end of step i).

[0054] The shaping step i) can be carried out by extrusion, pelletizing, agglomeration or spheronization.

[0055] Said zeolitization step (ii) can be carried out by heat treatment in the presence of water or a potassium hydroxide solution under autogenous pressure in a closed reactor.

[0056] In one embodiment, said shaped partially zeolitic material may be brought into contact with water or a potassium hydroxide solution in liquid form by immersion.

[0057] In another embodiment, said shaped partially zeolitic material may be contacted with water or a solution of potassium hydroxide in vapor form.

[0058] The zeolitic material obtained after the zeolitization of step ii) can be washed several times with water to obtain a final pH in the washing waters of between 7 and 8, then can be dried at a temperature of between 80 and 130°C, preferably between 90 and 120°C, very preferably around 100°C, for 1 to 24 hours.

[0059] The process may comprise a step iii) of calcining the zeolitic microporous material at a temperature of between 300 and 550°C for a period of between 2 and 6 hours, after the zeolitization step(s) ii).

[0060] In one embodiment, the zeolithizable binder consists of a mixture of an alumina source and a silica source, preferably the alumina source may be aluminum hydroxide, and the silica source may be colloidal silica.

[0061] In another embodiment, the zeolithizable binder consists of a zeolithizable clay known to those skilled in the art (for example kaolin or metakaolin), optionally mixed with another source of silica and / or another source of alumina.

[0062] The process for synthesizing the zeolitic microporous material according to the invention is carried out in the presence of potassium hydroxide, introduced either in step i) (by adding potassium hydroxide to the shaping or by impregnation of an aqueous solution of potassium hydroxide on the shaped product obtained in step i) dried and / or calcined), or in step ii) of zeolitization, or in both steps.

[0063] The invention also relates to the use of the zeolitic microporous material obtained according to any one of the variants of the preparation process as adsorbent, support or separation agent.

[0064] i) Shaping step

[0065] The first step of the process is a step of shaping the KL zeolite in a mixture with at least one zeolitizable binder, optionally water if necessary, and optionally a potassium hydroxide solution to obtain a partially zeolitic material shaped into extrudates, tablets or beads.

[0066] The content of KL zeolite in the shaped mixture (also called partially zeolitic material) is advantageously at least 60%, preferably between 60 and 80% relative to the dry matter.

[0067] The quantity of potassium hydroxide introduced during shaping is chosen to obtain a molar ratio between the silica contained in the zeolithizable binder considered in its oxide form SiO2 and the potassium hydroxide considered in its oxide form K2O of between: 3 and 10, preferably between 3.5 and 8 inclusive. This molar ratio is called (SiO2 / K2O)mef.

[0068] The zeolithizable binder may be, for example, kaolin, metakaolin or any other zeolithizable clay known to those skilled in the art, or mixtures of silicon and aluminum sources. The silicon source may be any of said sources commonly used for the synthesis of zeolites, for example powdered silica, silicic acid, colloidal silica, dissolved silica or tetraethoxysilane (TEOS). Among the powdered silicas, precipitated silicas may be used, in particular those obtained by precipitation from an alkali metal silicate solution, pyrogenic silicas, for example "CAB-O-SIL"™ (Cabot Corporation, USA), sodium silicate silica gels or clays such as kaolin or metakaolin.Colloidal silicas having different particle sizes, for example with an average equivalent diameter of between 10 and 15 nm or between 40 and 50 nm, such as those marketed under registered trademarks such as "LUDOX"™ (Sigma Aldrich, USA), may be used. Mixtures of the sources mentioned above may also be used. Preferably, the source of silicon is a colloidal silica.

[0069] The source of aluminum may preferably be aluminum hydroxide or an aluminum salt, for example chloride, nitrate, or sulfate, a sodium aluminate, or clays such as kaolin or metakaolin, an aluminum alkoxide, or alumina itself, preferably in hydrated or hydratable form, such as for example colloidal alumina, pseudoboehmite, gamma alumina or alpha or beta trihydrate. Mixtures of the sources cited above may also be used. Preferably, the source of aluminum is aluminum hydroxide.

[0070] The formulation may optionally comprise at least one organic adjuvant. In the case where said material comprises at least one organic adjuvant, said organic adjuvant is advantageously chosen from cellulose derivatives, polyethylene glycols, aliphatic monocarboxylic acids, aromatic compounds alkylated, sulfonic acid salts, fatty acids, polyvinyl pyrrolidone, polyvinyl alcohol, methylcellulose, polyacrylates, polymethacrylates, polyisobutene, polytetrahydrofuran, starch, polysaccharide-type polymers (such as xanthan gum), scleroglucan, hydroxyethylated cellulose derivatives, carboxymethylcellulose, lignosulfonates and galactomannan derivatives, taken alone or in mixture. Said organic adjuvant can also be chosen from all the additives known to those skilled in the art.

[0071] The shaping can be carried out by any method known to those skilled in the art, such as, for example, extrusion, pelletizing, agglomeration or spheronization. The water content of the mixture is adapted according to its constituents to obtain a mixture which allows easy shaping, usually between 10 and 60% by weight. For example, for pelletizing, the water content (loss on ignition, LOI) can be between 10 and 25%, in the case of shaping by extrusion, the water content (LOI) can be between 35 and 60% and for shaping by agglomeration, the water content (LOI) can be between 15 and 40%.

[0072] At the end of the shaping step, the material may optionally be dried and / or calcined and it may optionally be impregnated with a potassium hydroxide solution, in particular in the case where no source of potassium has yet been introduced during shaping.

[0073] The drying may be gentle drying, carried out at a temperature of between 60 and 95°C, preferably between 75 and 90°C for a period of between 1 and 24 hours, preferably between 2 and 12 hours, for example for 8 hours. The calcination may be carried out at temperatures of between 300 and 550°C for a period of between 2 and 8 hours.

[0074] The quantity of potassium hydroxide possibly introduced by impregnation is advantageously chosen to obtain a molar ratio between the silica source of the zeolithizable binder considered in its oxide form SiO2 and the potassium hydroxide considered in its oxide form K2O of between 3 and 5, preferably between 3.5 and 4 inclusive. This molar ratio is called (SiO2 / K2O);. The quantity of water necessary to prepare the potassium hydroxide solution is equal to the free pore volume of the shaped and dried and / or calcined material. The determination of the pore volume can be carried out for example by adding water drop by drop to 1 gram of shaped, dried and / or calcined material until the water is no longer adsorbed. The volume of water added is the free pore volume of the shaped, dried and / or calcined material per gram of material.

[0075] When potassium hydroxide is introduced in step i), during shaping and / or by impregnation, the total quantity of potassium hydroxide introduced in step i) is advantageously chosen to obtain a molar ratio between the silica source of the zeolitizable binder considered in its oxide form SiO2 and potassium hydroxide considered in its oxide form K2O between 3 and 5.

[0076] ii) zeolitization step

[0077] In this step, the partially zeolitic material shaped in step i) and advantageously containing at least 60%, preferably between 60 and 80% of KL zeolite by weight relative to the dry matter, is subjected to temperatures of between 95 and 200°C, preferably between 120 and 190°C, even more preferably between 150 and 180°C for a period of 5 to 72 hours, preferably 10 to 24 hours in the presence of water in vapor or liquid form, or in the presence of an aqueous solution of potassium hydroxide in vapor or liquid form to obtain a zeolitic microporous material shaped into extrudates, beads or tablets containing at least 90% of KL zeolite and having a mechanical strength greater than or equal to 0.7 daN / mm.

[0078] The treatment in the presence of water or an aqueous solution of potassium hydroxide can be carried out continuously (under flow in a licked or crossed bed reactor).

[0079] The treatment in the presence of water or an aqueous solution of potassium hydroxide can also be carried out statically in a closed reactor and under autogenous pressure, the water or the aqueous solution of potassium hydroxide being in liquid form or in vapor form. In the variant according to which the contact is made with water (possibly containing potassium hydroxide) in vapor form, the shaped mixture is generally in a basket suspended in the reactor without coming into direct contact with the liquid water (possibly containing potassium hydroxide) used for the generation of water vapor at autogenous pressure. In another variant, the treatment with liquid water (possibly containing potassium hydroxide) is carried out in a reactor under autogenous pressure in which the mixture shaped in step i) is immersed in the liquid.

[0080] The quantity of potassium hydroxide optionally introduced in step ii) of zeolitization is advantageously chosen to obtain a molar ratio between the silica source of the zeolitizable binder considered in its oxide form SiO2 and the potassium hydroxide considered in its oxide form K2O of between 0.5 and 5, preferably between 0.7 and 4 inclusive. This molar ratio is called (SiO2 / K2O)z.

[0081] In the case where the extrudates are brought into contact with a potassium hydroxide solution during step ii), the total quantity of potassium hydroxide introduced in steps i) and ii) is chosen to obtain a molar ratio between the silica source of the zeolithizable binder considered in its oxide form SiO2 and the potassium hydroxide considered in its oxide form K2O of between 3 and 5.

[0082] At the end of the treatment in the presence of water, the material is washed and dried.

[0083] Advantageously, the material can be washed several times with water, to preferably obtain a final pH in the washing waters of between 7 and 8. Then the material can be dried, preferably at a temperature of between 80 and 130°C, very preferably between 90 and 120°C for 1 to 24 hours, preferably between 2 and 12 hours, for example for 8 hours.

[0084] iii) Calcination step

[0085] At the end of step ii), a step iii) of calcination of the zeolitic microporous material may optionally be carried out at temperatures between 300 and 550°C for a duration of time between 2 and 8 hours. A calcined zeolitic microporous material is then obtained.

[0086] Characterization of the obtained zeolitic microporous material

[0087] The mechanical strength of the extrudates, balls or tablets obtained by the preparation process according to the invention, i.e. a grain crushing strength (EGG), is measured according to the ASTM D 4179-01 standard for balls and tablets or ASTM D 6175-03 for extrudates. This is a standardized test (ASTM D4179-01 standard) which consists of subjecting a material in the form of a millimetric object, such as a ball, a pellet or an extrudate, to a compressive force generating rupture. This test is therefore a measurement of the tensile strength of the material. The analysis is repeated on a certain number of individual solids and typically on a number of solids between 10 and 200. The average of the measured lateral breaking forces constitutes the average EGG which is expressed in the case of granules in units of force (N), and in the case of extrudates in units of force per unit of length (daN / mm or decaNewton per millimeter of extrudate length).According to the invention, the microporous zeolitic material obtained has a mechanical resistance thus measured greater than or equal to 0.7 daN / mm.

[0088] The molar quantities of the different elements present in the microporous zeolitic material obtained can be determined by the X-ray fluorescence method. The method makes it possible in particular to determine the Si / Al molar ratio of the microporous zeolitic material obtained. For a pure KL zeolite, the Si / Al molar ratio is generally between 2.8 and 4.3, excluding the upper limit.

[0089] X-ray fluorescence (XRF) spectrometry is a chemical analysis technique using a physical property of matter, X-ray fluorescence. It allows the analysis of the majority of chemical elements from Beryllium (Be) in concentration ranges from a few ppm to 100%, with accurate and reproducible results. X-rays are used to excite the atoms in the sample, causing them to emit X-rays with energies characteristic of each element present. The intensity and energy of these X-rays are then measured to determine the concentration of the elements in the material. X-ray diffraction X-ray diffraction allows to verify that the shaped solid obtained by the process according to the invention is indeed a KL zeolite of structural type LTL by comparing the diffractogram obtained with those existing in a database such as for example the crystallographic database PDF4+ 2020 of the ICDD. The purity obtained can advantageously be greater than or equal to 90%. The X-ray diffraction diagram is obtained by radiocrystallographic analysis by means of a diffractometer using the classic powder method with the Kai radiation of copper (X = 1.54060Â). From the position of the diffraction peaks represented by the angle 20, the characteristic reticular equidistances d^i of the sample are calculated by the Bragg relation. The measurement error A(dhki) on d^i is calculated using the Bragg relation as a function of the absolute error A (20) assigned to the measurement of 20. An absolute error A (20) equal to ± 0.02° is commonly accepted.The relative intensity Irei assigned to each dhki value is measured from the height of the corresponding diffraction peak. Comparing the area of the most intense peaks corresponding to the KL zeolite in the angular range 2O-3O°20 also makes it possible to determine the percentage of KL zeolite present in the material by comparing the area of the peaks of the shaped zeolite with those of a reference KL zeolite using a method similar to ASTM D3906 03, by comparing the areas of the peaks at angles (20) 22.65 ± 0.15 (hkl: 221); 24.27 ± 0.15 (hkl: 102); 25.56 ± 0.15 (hkl: 112); 27.12 ± 0.15 (hkl: 321); 28.00 ± 0.1 (hkl: 500) and 29.06 ± 0.15 (hkl: 302). The calculation formula used is as follows: .

[0090] %KL = (Sx / Sr)*100

[0091] Where %KL is the mass percentage of zeolite KL contained in the material.

[0092] Sx is the total area of the peaks at angles (20) 22.65 ± 0.15 (hkl: 221); 24.27 ± 0.15 (hkl: 102); 25.56 ± 0.15 (hkl: 112); 27.12 ± 0.15 (hkl: 321); 28.00 ± 0.1 (hkl: 500) and 29.06 ± 0.15 (hkl: 302) of the sample to be analyzed.

[0093] Sr is the total area of the peaks at angles (20) 22.65 ± 0.15 (hkl: 221); 24.27 ± 0.15 (hkl: 102); 25.56 ± 0.15 (hkl: 112); 27.12 ± 0.15 (hkl: 321); 28.00 ± 0.1 (hkl: 500) and 29.06 ± 0.15 (hkl: 302) of the reference sample (pure KL zeolite).

[0094] The invention is illustrated by the following examples which are in no way limiting. EXAMPLES

[0095] Example 1: preparation of a reference sample based on pure KL zeolite

[0096] 7.484 g of potassium hydroxide (KOH, Aldrich purity 99% by mass) are dissolved in 48.667 g of distilled water until the solution is clear. Into this aqueous solution of potassium hydroxide (KOH) are added with stirring 4.628 g of aluminum hydroxide (MERCK amorphous gel, 57.55% A12O3). The mixture is then homogenized for 15 minutes and then 39.221 g of LUDOX HS40 (DUPONT, 40% SiO2) are added, still stirring. The mixture is then homogenized for 5 minutes to obtain a gel. The gel obtained is then transferred to a 160 mL Teflon-lined autoclave. The autoclave is heated to 180°C for 48 hours without stirring. After crystallization, the autoclave is cooled to room temperature. The suspension containing the KL zeolite is filtered and then washed on the filter with distilled water until the pH of the liquid is close to 7. The KL zeolite obtained is dried for 12 hours at 100°C to obtain a powder. Analysis of the powder by X-ray diffraction (XRD) confirms the production of a pure KL zeolite ([Fig. 1]). The Si / Al molar ratio measured by X-ray fluorescence of the KL zeolite obtained according to example 1 is 3.15.The loss on ignition (LOI) of KL zeolite after drying is 10%. The pure KL zeolite obtained in this example is also used as a reference sample.

[0097] Example 2: (according to the invention): preparation of a material shaped by extrusion and containing at least 90% by weight of KL zeolite

[0098] 83.33 g of KL zeolite obtained according to example 1 having a PAF of 10% are mixed with 38.05 g of LUDOX AS40 silica sol (DUPONT, 40% SiO2), 4.49 g of aluminum hydroxide (MERCK amorphous gel, 57.55% A12O3), 7.33 g of potassium hydroxide (KOH, Aldrich purity 99% by mass) and 50 g of water. The molar ratio between the silica contained in the zeolithizable binder considered in its SiO2 oxide form and the potassium considered in its K2O oxide form (SiO2 / K2O)mef is 3.9. The mixture is mixed for 20 minutes in a z-arm mixer and then extruded with a piston extruder to obtain extrudates of 2 mm in diameter.

[0099] Then the extrudates are introduced into a stainless steel basket which is suspended in a 1 liter stainless steel reactor containing 200 mL of water. The extrudates are not in contact with liquid water. The reactor is closed and heated to 180°C for 10 hours under autogenous pressure. Then the reactor is opened, the extrudates are recovered and washed 4 times with 400 mL of water each time. After washing, the extrudates are dried for 8 hours at 100°C. The extrudates are then introduced into a muffle furnace where a calcination step is carried out in air: the calcination cycle includes a temperature rise of 1.5°C / min up to 200°C, a hold at 200°C maintained for 2 hours, a temperature rise of 1°C / min up to 500°C followed by a hold at 500°C maintained for 8 hours and then a return to room temperature.The percentage of KL zeolite present in the extrudates determined by comparing the X-ray diffraction (XRD) pattern of the extrudates with that of the reference sample obtained according to Example 1 is 91%. The grain crushing strength of the extrudates obtained is 0.80 daN / mm.

[0100] Example 3 (according to the invention): preparation of a material shaped by extrusion and containing at least 90% by weight of KL zeolite

[0101] 83.33 g of KL zeolite obtained according to example 1 having a PAF of 10% are mixed with 38.05 g of LUDOX AS40 silica sol (DUPONT, 40% SiO2), 4.49 g of aluminum hydroxide (MERCK amorphous gel, 57.55% A12O3) and 50 g of water. The mixture is mixed for 20 minutes in a z-arm mixer and then extruded with a piston extruder to obtain extrudates of 2 mm in diameter. The extrudates obtained are dried for 12 hours at 80°C (the free pore volume determined by the method described in the present invention is 0.4 ml / g) and then impregnated with a solution containing 7.33 g of potassium hydroxide (KOH, Aldrich purity 99% by mass) and 40 ml of water. The molar ratio between the silica contained in the zeolitic binder considered in its oxide form SiO2 and the potassium considered in its oxide form K2O (SiO2 / K2O) is 3.9.

[0102] Then the extrudates are introduced into a stainless steel basket which is suspended in a 1 liter stainless steel reactor containing 200 mL of water. The extrudates are not in contact with liquid water. The reactor is closed and heated to 180°C for 10 hours under autogenous pressure. Then the reactor is opened, the extrudates are recovered and washed 4 times with 400 mL of water each time. After washing, the extrudates are dried for 8 hours at 100°C. The extrudates are then introduced into a muffle furnace where a calcination step is carried out in air: the calcination cycle includes a temperature rise of 1.5°C / min up to 200°C, a hold at 200°C maintained for 2 hours, a temperature rise of 1°C / min up to 500°C followed by a hold at 500°C maintained for 8 hours and then a return to room temperature.The percentage of KL zeolite present in the extrudates determined by comparing the DRX of the extrudates with that of the reference sample obtained according to example 1 is 93%. The grain crushing strength of the extrudates obtained is 0.79 daN / mm.

[0103] Example 4 (according to the invention): preparation of a material shaped by extrusion and containing at least 90% by weight of KL zeolite

[0104] 83.33 g of KL zeolite obtained according to example 1 having a PAF of 10% are mixed with 38.05 g of LUDOX AS40 silica sol (DUPONT, 40% SiO2), 4.49 g of aluminum hydroxide (MERCK amorphous gel, 57.55% A12O3) and 50 g of water. The mixture is mixed for 20 minutes in a z-arm mixer and then extruded with a piston extruder to obtain extrudates of 2 mm in diameter. The extrudates obtained are dried for 12 hours at 80°C. The extrudates are then introduced into a muffle furnace where a calcination step is carried out in air: the calcination cycle includes a temperature rise of 1.5°C / min up to 200°C, a plateau at 200°C maintained for 2 hours, a temperature rise of 1°C / min up to 500°C followed by of a plateau at 500°C maintained for 8 hours then a return to room temperature.

[0105] Then the extrudates are introduced into a stainless steel basket which is suspended in a 1 liter stainless steel reactor containing 200 mL of a 3 molar solution of potassium hydroxide. The molar ratio between the silica contained in the zeolithizable binder considered in its oxide form SiO2 and the potassium considered in its oxide form K2O (SiO2 / K2O)z is 0.84.

[0106] The extrudates are not in contact with the potassium hydroxide solution. The reactor is closed and heated to 185°C for 10 hours under autogenous pressure. Then the reactor is opened, the extrudates are recovered and washed 4 times with 400 mL of water each time. After washing, the extrudates are dried for 8 hours at 100°C. The extrudates are then introduced into a muffle furnace where a calcination step is carried out in air: the calcination cycle includes a temperature rise of 1.5°C / min up to 200°C, a plateau at 200°C maintained for 2 hours, a temperature rise of 1°C / min up to 500°C followed by a plateau at 500°C maintained for 8 hours and then a return to room temperature. The percentage of KL zeolite present in the extrudates determined by comparing the DRX of the extrudates with that of the reference sample obtained according to Example 1 is 94%. The grain crushing strength of the extrudates obtained is 0.80 daN / mm.

[0107] Example 5 (according to the invention): preparation of a material shaped by extrusion and containing at least 90% by weight of KL zeolite)

[0108] 112.44 g of KL zeolite obtained according to example 1 having a PAF of 10% are mixed with 70.48 g of LUDOX AS40 silica sol (DUPONT, 40% SiO2), 17.32 g of metakaolin (CLAYRAC kaolin calcined at 600°C; Si / Al = 1.2), and 7.65 g of water. The mixture is mixed for 20 minutes in a z-arm mixer and then extruded with a piston extruder to obtain extrudates of 2 mm in diameter. The extrudates obtained are dried for 12 hours at 80°C. The extrudates are then introduced into a muffle furnace where a calcination step is carried out in air: the calcination cycle includes a temperature rise of 1.5°C / min up to 200°C, a hold at 200°C maintained for 2 hours, a temperature rise of 1°C / min up to 500°C followed by a hold at 500°C maintained for 8 hours and then a return to room temperature.

[0109] Then the extrudates are introduced into a stainless steel basket which is suspended in a 1 liter stainless steel reactor containing 400 mL of a 3 molar solution of potassium hydroxide. The molar ratio between the silica contained in the zeolithizable binder considered in its oxide form SiO2 and the potassium considered in its oxide form K2O (SiO2 / K2O)z is 0.8.

[0110] The extrudates are not in contact with the potassium hydroxide solution. The reactor is closed and heated to 175°C for 48 hours under autogenous pressure. Then the reactor is opened, the extrudates are recovered and washed 4 times with 400 mL of water each time. After washing, the extrudates are dried for 8 hours at 100°C. The extrudates are then introduced into a muffle furnace where a calcination step is carried out in air: the calcination cycle includes a temperature rise of 1.5°C / min up to 200°C, a hold at 200°C maintained for 2 hours, a temperature rise of 1°C / min up to 500°C followed by a hold at 500°C maintained for 8 hours and then a return to room temperature. The percentage of KL zeolite present in the extrudates determined by comparing the DRX of the extrudates with that of the reference sample obtained according to Example 1 is 93%. The grain crushing strength of the extrudates obtained is 0.90 daN / mm.

[0111] Example 6 (according to the invention): preparation of a material shaped by pelletizing and containing at least 90% by weight of KL zeolite

[0112] 83.33 g of KL zeolite obtained according to example 1 having a PAF of 10% are mixed with 38.05 g of LUDOX AS40 silica sol (DUPONT, 40% SiO2), 4.49 g of aluminum hydroxide (MERCK amorphous gel, 57.55% A12O3), 7.33 g of potassium hydroxide (KOH, Aldrich purity 99% by mass). The molar ratio between the silica contained in the zeolithizable binder considered in its oxide form SiO2 and the potassium considered in its oxide form K2O (SiO2 / K2O)mef is 3.9.

[0113] The mixture is kneaded for 20 minutes in a z-arm mixer and then shaped by tableting to obtain tablets 2 mm in diameter.

[0114] Then the tablets are introduced into a stainless steel basket which is suspended in a 1 liter stainless steel reactor containing 200 mL of water. The tablets are not in contact with liquid water. The reactor is closed and heated to 180°C for 10 hours under autogenous pressure. Then the reactor is opened, the tablets are recovered and washed 4 times with 400 mL of water each time. After washing, the tablets are dried for 8 hours at 100°C. The tablets are then introduced into a muffle furnace where a calcination step is carried out in air: the calcination cycle includes a temperature rise of 1.5°C / min up to 200°C, a hold at 200°C maintained for 2 hours, a temperature rise of 1°C / min up to 500°C followed by a hold at 500°C maintained for 8 hours and then a return to room temperature.The percentage of KL zeolite present in the tablets determined by comparing the DRX of the extrudates with that of the reference sample obtained according to example 1 is 92%. The grain crushing strength of the extrudates obtained is 0.78 daN / mm.

[0115] Example 7 (comparative): preparation of a material shaped by extrusion and containing at least 90% by weight of KL zeolite.

[0116] In this example, a material is prepared by a method similar to Example 1 of patent US5354933 to obtain a material containing 90% by weight of KL zeolite. 90g of KL zeolite obtained according to Example 1 are mixed with 25g of sol of LUDOX HS40 silica (DUPONT, 40% SiO2). The mixture is kneaded and then extruded with a piston extruder to obtain extrudates of 2 mm in diameter. The extrudates are then introduced into a muffle furnace where a calcination step is carried out in air at 500°C for 2 hours. The grain crushing strength of the extrudates obtained is less than 0.2 daN / mm, significantly lower than the values obtained for Examples 2-6 according to the invention.

Claims

Claims

1. Process for preparing a microporous zeolitic material shaped in the form of extrudates, tablets or beads having a mechanical crushing strength greater than or equal to 0.7 daN / mm and containing at least 90% by mass of KL zeolite of LTL structural type, comprising: i) a step of shaping a KL zeolite powder, mixed with at least one zeolithizable binder, in the presence or absence of potassium hydroxide, to obtain extrudates, tablets or beads of partially zeolitic material;ii) at least one step of zeolitization of said shaped partially zeolitic material from step i) by contacting with water in vapor form or with an aqueous solution of potassium hydroxide in vapor form, at a temperature of between 95 and 200°C for a period of between 5 and 72 hours, washing, then drying in order to obtain a microporous zeolitic material in the form of extrudates, tablets or beads containing at least 90% by mass of KL zeolite, and having a mechanical crushing strength greater than or equal to 0.7 daN / mm, the potassium hydroxide being introduced in step i) and / or in step ii).;

2. Preparation process according to claim 1, wherein said at least one zeolithizable binder is chosen from kaolin, metakaolin or a zeolithizable clay, or mixtures of silica and alumina such as colloidal silica, pyrogenic silicas, sodium silicate, sodium aluminate, boehmites or aluminum hydroxide, alone or as a mixture.

3. Preparation process according to one of the preceding claims, in which the shaping is carried out by extrusion, pelletizing, agglomeration or spheronization.

4. Preparation process according to one of the preceding claims, in which step i) comprises gentle drying of the extrudates, beads or shaped tablets at a temperature between 60 and 95°C, preferably between 75 and 90°C for a period of between 1 and 24 hours.

5. A preparation process according to claim 4, wherein said drying is followed by calcination of the dried extrudates, beads or tablets at a temperature between 300 and 550°C for a duration between 2 and 8 hours.

6. Preparation process according to one of claims 4 or 5, in which the dried and optionally calcined extrudates, balls or tablets are impregnated with a potassium hydroxide solution before step ii) of zeolitization.

7. Preparation process according to one of the preceding claims, in which said zeolitization step ii) is carried out by heat treatment in the presence of water or a potassium hydroxide solution under autogenous pressure in a closed reactor.

8. Preparation process according to one of the preceding claims, in which the zeolitic material obtained after the zeolitization of step ii) is washed several times with water to obtain a final pH in the washing waters of between 7 and 8, then dried at a temperature of between 80 and 130°C, preferably between 90 and 120°C for 1 to 24 hours, preferably between 2 and 12 hours.

9. Preparation process according to one of the preceding claims, in which the process comprises a step iii) of calcining the extrudates, beads, tablets of zeolitic microporous material obtained in step ii) at a temperature of between 300 and 550°C for a period of between 2 and 8 hours, after the zeolitization step(s) ii).

10. Preparation process according to one of the preceding claims, in which the zeolithizable binder comprises a source of alumina which is aluminum hydroxide, and a source of silica which is a colloidal silica.

11. Preparation process according to one of the preceding claims, in which the zeolithizable binder comprises kaolin or meta kaolin.

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