Process for the synthesis of a new IZM-11 core-layer composite zeolite material of CHA structural type with a Si / Al composition gradient.

Abstract

The present invention relates to a new process for preparing an IZM-11 core-layer zeolite of CHA structural type, making it possible to carry out the synthesis of a zeolite material of IZM-11 core-layer zeolite type of CHA structural type with Si / Al gradient, in which - the SiO2 / Al2O3 molar ratio of the core is between 8 and 30, - the SiO2 / Al2O3 molar ratio of the layer is at least 160. Figure to be published: Figure 3

Description

Title of the invention: Process for the synthesis of a new IZM-11 core-layer composite zeolitic material of CH A structural type having a Si / Al composition gradient. Technical field

[0001] The present invention relates to a new method for synthesizing a composite zeolitic material based on an IZM-11 zeolite of CHA structural type having a Si / Al composition gradient between the core and the layer.

[0002] Said IZM-11 zeolite of CHA structural type obtained according to the process of the invention advantageously finds its application as a catalyst, adsorbent or separation agent, in particular for depollution, in particular automotive, for the selective catalytic reduction of NOx in the presence of a reducing agent. Prior art

[0003] Crystallized microporous materials, such as zeolites or silicoalumino-phosphates, are solids widely used in industry as catalysts, catalyst supports, adsorbents or separation agents.

[0004] Zeolites are generally prepared from an aqueous synthesis gel containing a source of silicon oxides, aluminum, mineralizing agent and a structuring agent.

[0005] CHA structural type zeolites have a three-dimensional system of pores delimited by eight TO4 tetrahedra and obtained by the three-dimensional connection of double cycles of T atoms (D6R) where T can be silicon, aluminum or phosphorus. Many methods for synthesizing CHA structural type zeolites are known. CHA structural type zeolites synthesized from N,N,N-trimethyl-l-adamantamonium include in particular SSZ-13, SSZ-23, SSZ-24, SSZ-25 and SSZ-31 zeolites (Y. Nakagawa et al., Microporous and Me-soporous Materials, 22, 69-85 (1998)).

[0006] Core-layer zeolites are defined as composite materials formed from at least two different materials, organized in such a way that the zeolite (outer) layer entirely encompasses the zeolite (inner) core (Valtchev et al., Adv. Funct. Mater., 15, 1955 (2005)).

[0007] Si / Al gradient zeolites are composite zeolite materials defined as core-layer zeolites having a core and a layer having the same structural type, but having a different Si / Al ratio. There are many examples in the literature of synthesizing Si / Al gradient core-layer zeolite on MFI structural type zeolite (M. Miyamoto et al., Microporous and Mesoporous Materials, 115,106-112 (2008); Chen et al., Catal. Lett., 136, 65-70 (2010)). The BEA-structured zeolite has also been recently studied to prepare a Si / Al gradient core-layer zeolite of BEA-structured type (Rimer et al., Angewandte Chemie, 61, e202210434 (2022)).

[0008] Patent application US2019 / 0336954A1 describes a synthesis of a zeolite of the Chabazite CHA core-layer structural type in a basic medium. A first core zeolite is synthesized, for example in the presence of N,N,N-trimethyl-l-adamantamonium, with a SiO2 / Al2O3 molar ratio (also called in the text by the acronym SAR) of less than 25, in the form of grains. This first core zeolite is immersed in a synthesis gel containing the precursors allowing the formation of a second zeolite of the Chabazite CHA structural type with a SAR of at least 25, forming in the form of a layer covering all or part of the surface of the grains of the first Chabazite, by deposition or growth. The layer of the second Chabazite is indicated as having more Bronsted acid sites than the core consisting of the first Chabazite.

[0009] In this document, the first core zeolite may be of type SSZ-13 while the second layer zeolite may be of type SSZ-25. The different SARs are measured by SEM (scanning electron microscope) and EDS (energy dispersive X-ray spectroscopy) analyses, and no layer thickness is specified.

[0010] This document also recommends carrying out a dealumination of the core-layer zeolite thus formed, in particular by acid treatment, and an impregnation or ion exchange with a salt solution of a metal such as Cu, Fe, Co, Zr or Ti.

[0011] The article entitled “Effect of core-shell structuring of chabazite zeolite with a siliceous zeolite thin layer on the separation of acetone-butanol-ethanol vapor in humid vapor conditions” (Miyamoto et al., Chemical Engineering Journal, 363, 292-299 (2019)) presents the synthesis of a core-shell CHA structural type SSZ-13 zeolite in fluoride medium. The core zeolite is synthesized in fluoride medium in the presence of N,N,N-trimethyl-l-adamantamonium, purified and calcined, with a SAR of 78.6. The core zeolite is immersed in a synthesis gel containing the precursors allowing the formation of a purely silicic CHA structural type zeolite. The different SARs are measured by SEM (scanning electron microscope) and EDS (energy dispersive X-ray spectroscopy) analyses. The layer thickness is estimated at 100 nm for a core-layer zeolite size of 40.6 qm.

[0012] The aim of the invention is to develop a new type of IZM-11 zeolite of CHA core-layer structural type with Si / Al gradient, which has improved properties, as well as a new method of preparing it. The aim is in particular to obtain such a zeolite with improved properties, particularly in terms of reactivity when an application as a ca- talyser is targeted. Description of the invention

[0013] Surprisingly, it has been discovered in the present invention that it is possible to obtain a CHA structural type zeolite having a Si / Al composition gradient of great difference between the core and the layer, much higher than the gradients described in the prior art. In other words, it has been discovered that it is possible to obtain a CHA core-layer type zeolite, with a very different SiO2 / Al2 O3 molar ratio (SAR) in the layer and in the core, and in particular with a much higher SAR in the layer than in the core. It has thus been possible to observe layer SAR / core SAR ratios of at least 10, in particular at least 50, 70 or even at least 80.

[0014] According to the invention, the core zeolite of structural type CHA according to the invention preferably has a SAR less than or equal to 30, more preferably less than or equal to 20.

[0015] It is preferably synthesized in a basic medium, then immersed in a synthesis gel in a basic medium containing the precursors allowing the formation of a layer of zeolite of CHA structural type with a SAR greater than or equal to 160, and even greater than or equal to 180 or greater than or equal to 200. In the zeolite obtained according to the invention, the layer therefore has a SiO2 / Al2O3 molar ratio (SAR) greater than or equal to 160 and the core with a SiO2 / Al2O3 molar ratio (SAR) less than or equal to 30, more preferably less than 20.

[0016] The process according to the invention is flexible: it allows in particular the synthesis of these core-layer zeolites with variable layer thicknesses. Summary of the invention

[0017] The new process according to the invention makes it possible to obtain an IZM-11 core-layer zeolite with a Si / Al gradient of the Chabazite (CHA) structural type (in a basic medium), with a core with a SiO2 / Al2O3 ratio much lower than the SiO2 / Al2O3 ratio of the layer.

[0018] In more detail, the invention firstly relates to a process for preparing a zeolitic material of the IZM-11 core-layer zeolite type with a Si / Al gradient of the CHA structural type comprising at least the following steps: i) the mixture in aqueous medium of a source of silicon, a source of aluminum, an organic nitrogen compound R, R being N,N,N-trimethyl-1-adamantamonium, and sodium hydroxide, the reaction mixture having the following molar composition: H2O / SiO2 between 40 and 100, preferably between 40 and 60 SiO2 / Al2O3 between 160 and infinity, preferably between 180 and 240 SiO2 / R between 5 to 20, preferably between 7 and 10 SiO2 / Na2O between 5 and 50, preferably between 8 and 15 in which Na2O denotes the quantity of Na2O provided by the soda, SiO2 denotes the quantity of SiO2 provided by the silicon source, and Al2O3 denotes the quantity of A12O 3 provided by the aluminum source, until a homogeneous precursor gel is obtained; ii) the addition of a zeolite in powder form, of CHA structural type with a SiO2 / Al2O3 SAR molar ratio of between 8 and 30, preferably between 10 and 14, until a homogeneous suspension is obtained, with a SiO2 / zeolite (powder) mass ratio of between 0.2 and 11, preferably between 0.5 and 7 iii) the hydrothermal treatment of said precursor gel obtained at the end of step ii) at a temperature between 130°C and 180°C, for a period between 2 hours and 8 days until a core-layer zeolite with a Si / Al gradient IZM-11 of CHA structural type is obtained with a molar ratio value SiO2 / Al2O3 - less than or equal to 30, in particular between 8 and 30, for the heart - and at least 160, in particular at least 180 or at least 200 for the layer. iv) Washing the gel obtained at the end of step iii) with distilled water until a solution is obtained after washing with a pH between 7 and 8 v) Drying the wet solid obtained from step iv) for a period of between 4 hours and 24 hours at a temperature of between 20 and 150°C. vi) Optional calcination of the dried solid obtained from step v), in particular at a temperature of between 420°C and 600°C for a period of between 6 hours and 16 hours, the calcination possibly being preceded by a gradual increase in temperature.

[0019] Preferably, the overall SiO2 / Al2O3 molar ratio of the IZM-11 zeolite of CHA structural type obtained is between 16 and 120, preferably between 20 and 85.

[0020] Preferably, step i) comprises a step of maturing the reaction mixture at a temperature of between 15 and 35°C, with stirring, for a period of between 2 h and 8 h, preferably between 3 h and 5 h.

[0021] Preferably, the CHA structural type zeolite added in powder form to the reaction medium in step ii) has a particle size of between 50 nm and 10 pm, preferably between 100 nm and 3 pm.

[0022] Preferably, the hydrothermal treatment of step iii) is carried out under autogenous pressure at a temperature of between 150°C and 165°C, for a period of between 2 days and 7 days, and preferably between 4 days and 6 days.

[0023] Preferably, the solid phase obtained at the end of step iii) is filtered, washed, and dried at a temperature between 60 and 100°C, for a period between 4 hours and 24 hours to obtain a dried zeolite.

[0024] The invention also relates to the zeolitic material of the core-layer zeolite type IZM-11 of CHA structural type with Si / Al gradient obtained by the pre- preparation described above.

[0025] The invention also relates to the zeolitic material of the core-layer zeolite type IZM-11 of CHA structural type with Si / Al gradient, in particular obtained by the preparation process described above, in which - the SiO2 / Al2O3 molar ratio of the core is between 8 and 30, - the SiO2 / Al2O3 molar ratio of the layer is at least 160 - and wherein the layer has a thickness of between 10% and 200% growth percentage, preferably between 20% and 150% growth percentage.

[0026] The growth percentage is defined by the following formula:

[0027] growth percentage = 100 x -1)

[0028] The percentage of growth therefore depends on the initial morphology of the heart.

[0029] The composite zeolite material of the core-layer zeolite type IZM-11 of the type CHA structural with Si / Al gradient according to the invention can have a SiO2 / A12O3 molar ratio of the layer which is infinite: we are then in the case where the layer is purely silicic (or almost, depending on the detection limits of the analysis means).

[0030] The composite zeolite material of the IZM-11 core-layer zeolite type of CHA structural type with Si / Al gradient according to the invention may have a SiO2 / Al2O3 molar ratio of the layer of at least 200, and preferably of at most 800 or of at most 300.

[0031] The composite zeolite material of the IZM-11 core-layer zeolite type of CHA structural type with Si / Al gradient according to the invention may have a SiO2 / Al2O3 molar ratio of the core of at most 20, and is in particular between 10 and 14.

[0032] The composite zeolite material of the core-layer zeolite type IZM-11 of CHA structural type with Si / Al gradient according to the invention may have an ASAr ratio of the SiO2 / Al2O3 molar ratio of the layer to the SiO2 / Al2O3 molar ratio of the core of at least 10, in particular of at least 20 or at least 50, or of at least 70 or at least 80.

[0033] The composite zeolite material of the IZM-11 core-layer zeolite type of CHA structural type with Si / Al gradient according to the invention may comprise at least the following X-ray diffraction lines:

[0034] [Tables 1] 2 theta (°) Irel 2 theta (°) Irel 9.598 FF 26.225 f 13.055 mf 27.877 ff 14.144 ff 28.345 ff 16.217 f 29.973 ff 17.977 f 30.89 mf 19.299 ff 31.096 mf 20.797 m 31.324 mf 22.232 ff 32.782 ff 22.762 ff 33.819 ff 23.269 ff 34.833 ff 25.243 f 36.393 ff

[0035] where FF = very strong; F = strong; m = medium; mf = medium weak; f = weak; ff = very weak. The relative intensity Irei is given in relation to a relative intensity scale where a value of 100 is assigned to the most intense line in the X-ray diffraction pattern: ff <15; 15 <f <30 ; 30 < mf <50 ; 50 <m < 65 ; 65 <F < 85 ; FF >85.

[0036] The composite zeolite material of the IZM-11 core-layer zeolite type of CHA structural type with Si / Al gradient according to the invention may have a purity greater than or equal to 97%, in particular greater than or equal to 98 or 99%.

[0037] The composite zeolite material of the IZM-11 core-layer zeolite type of CHA structural type with Si / Al gradient according to the invention may be such that the layer has a more hydrophobic character than the core.

[0038] The invention also relates to the application of the composite zeolite material of the core-layer zeolite type IZM-11 of CHA structural type with Si / Al ratio gradient as defined above, as a catalyst, molecular sieve or adsorbent.

[0039] Note that within the meaning of the invention, the layer may completely cover the outer surface of the core, or only partially cover the surface. The thickness of the layer may not be constant around the core, in particular depending on the morphology of the core. List of figures

[0040] [Fig. 1] represents the X-ray powder diffractogram obtained from the material according to Example 1. The abscissa is given in 20 / degrees and the ordinate in arbitrary intensity.

[0041] [Fig.2] represents the scanning electron microscopy image obtained from the material according to example 1.

[0042] [Fig. 3] represents the transmission electron microscopy image and its energy dispersive X-ray spectroscopy analysis obtained from the material according to Example 3.

[0043] Other characteristics and advantages of the synthesis process according to the invention, and of the zeolitic material thus obtained, will appear on reading the following description of non-limiting examples of embodiment, with reference to the figures appended and described below. Detailed description of the invention

[0044] It should be noted that throughout this text, the intervals, ranges of values / parameters / percentages stated are inclusive, unless explicitly stated otherwise. In the case of open intervals, the undefined limit can go up to + / - infinity.

[0045] The subject of the present invention is a new process for preparing a zeolitic material in the form of an IZM-11 core-layer zeolite of CHA structural type, comprising at least the steps set out above. Each of the preparation steps will be detailed below: Step i) of mixing

[0046] Step i) of mixing is carried out until a homogeneous mixture is obtained, preferably for a period greater than or equal to 5 minutes, preferably with stirring by any system known to those skilled in the art, at low, medium or high shear rate.

[0047] Step i) comprises mixing in an aqueous medium, a source of silicon, a source of aluminum, an organic nitrogen compound R, R being N,N,N-trimethyl-1-adamantamonium and sodium hydroxide, the reaction mixture having the following molar composition: H2O / SiO2 between 40 and 100, preferably between 40 and 60 SiO2 / Al2O3 between 160 and infinity, preferably between 180 and 240 SiO2 / R between 5 and 20, preferably between 7 and 10 SiO2 / Na2O between 5 and 50, preferably between 8 and 15 - in which Na2O denotes the quantity of Na2O provided by the soda. in which SiO2 denotes the quantity of silica provided by the silicon source (which can also be called silicic precursor) which can be silica fume, silicic acid, sodium silicate, silica gel, a colloidal suspension of silica or tetraethyl orthosilicate, more preferably tetraethyl orthosilicate and even more preferably a colloidal suspension of silica. - in which Al2O3 denotes the quantity of alumina supplied by the source aluminum (which can also be called aluminum precursor), which can be aluminum sulfate, sodium aluminate, alumina, aluminum hydroxide, aluminum hydroxide, preferably amorphous aluminum hydroxide.

[0048] The reaction mixture is stirred until a homogeneous precursor gel is obtained.

[0049] The silica source and / or the aluminum source may each be composed of one component or a plurality of components, in particular chosen from the lists above.

[0050] In accordance with the invention, R is the organic nitrogen compound N,N,N-trimethyl-1-adamantamonium, which acts as a structuring agent allowing the formation of the desired zeolitic material.

[0051] At the end of step i), a homogeneous precursor gel is obtained with a zeolite of CHA structural type in suspension.

[0052] It may be advantageous to carry out a ripening of the reaction mixture before the hydrothermal crystallization during said step i) of the process of the invention in order to control the size of the crystals of the zeolite of CHA structural type constituting the layer. This ripening advantageously promotes the primary nucleation of the layer seeds. The ripening of the reaction mixture during said step i) of the process of the invention may be carried out at room temperature, or at a temperature between 15 and 35°C, with stirring, for a duration advantageously between 2 hours and 8 hours.

[0053] It is also possible to provide for maturing of the mixture at the end of step ii) of adding zeolite. Step ii) adding the core zeolite

[0054] Step ii) comprises the addition of a zeolite powder (in particular SSZ-13) of CHA structural type with a SAR of between 8 and 30, preferably between 10 and 20, until a homogeneous suspension is obtained. This addition can be carried out in powder form (grains, seeds, crystals) as long as the source can be homogenized in the reaction medium obtained at the end of step i), under any stirring known to those skilled in the art, at room temperature or a temperature of between 10°C and 35°C. The SiO2 / zeolite powder mass ratio is between 0.2 and 11, preferably between 0.5 and 7.

[0055] In accordance with the invention, a CHA structural type zeolite having a SiO2 (cha / A12O3 (CHa) molar ratio of between 8 and 30, inclusive, is incorporated into the reaction mixture for the implementation of step (ii) as a source of the core of the CHA structural type zeolite core-layer with Si / Al gradient.

[0056] The starting CHA structural type zeolite having a SiO2 / Al2O3 molar ratio of between 8 and 30 can be obtained by any method known to those skilled in the art; it can also be commercial zeolites. Step iii) of hydrothermal treatment

[0057] In accordance with step (iii) of the process according to the invention, the precursor gel obtained at the end of step ii) is subjected to a hydrothermal treatment, preferably carried out at a temperature of between 130°C and 180°C for a period of between 2 hours and 8 days, until the zeolite (IZM-11) of the CHA core-layer structural type with a Si / Al gradient is formed.

[0058] The precursor gel is advantageously placed under hydrothermal conditions under an autogenous reaction pressure, at a temperature preferably between 130°C and 180°C, preferably between 150°C and 165°C, until the complete crystallization of an IZM-11 zeolite of CHA core-layer structural type with Si / Al gradient.

[0059] The time required to obtain crystallization varies between 2 hours and 8 days, preferably between 24 hours and 5 days.

[0060] The reaction is generally carried out with stirring or without stirring, preferably with stirring. As the stirring system, any system known to those skilled in the art can be used, for example a rotating arm system, inclined blades with counter-blades, stirring turbines, Archimedes screws. Step iv) washing and step v) drying

[0061] At the end of the reaction, after carrying out said step iii) of the preparation process according to the invention, the solid phase formed from the IZM-11 zeolite of CHA structural type is preferably filtered, washed and then dried.

[0062] The gel obtained at the end of step iii) is thus treated by repeated washing with distilled water until a solution is obtained after washing with a pH of between 7 and 8.

[0063] Drying is generally carried out at a temperature between 20 and 150°C, preferably between 60 and 100°C, for a period of between 4 and 24 hours.

[0064] Very preferably, the wet solid obtained at the end of step iv) is dried for a period of between 4 hours and 24 hours at 100°C, preferably between 8 and 12 hours. Step vi) optional calcination

[0065] The core-layer zeolite IZM-11 of CHA structural type, after the drying step, is then ready for subsequent steps such as calcination. For this step, all conventional methods known to those skilled in the art can be used.

[0066] The step of calcining the IZM-11 zeolite of CHA structural type obtained according to the process of the invention is preferably carried out at a temperature between 420 and 600°C for a duration between 6 and 16 hours. The dried solid obtained at the end of step v) can for example be calcined at 550°C for a duration of 8 hours.

[0067] The IZM-11 zeolite of CHA structural type obtained at the end of the calcination step is free of any organic species, and in particular of the organic structuring agent R.

[0068] At the end of said calcination step, X-ray diffraction makes it possible to verify that the solid obtained by the process according to the invention is indeed a zeolite of structural type CHA. The purity obtained is advantageously greater than 97% and preferably greater than or equal to 98% or 99%.

[0069] The solid obtained has the X-ray diffraction diagram including at least the lines present - in the zeolite (in the SSZ-13 examples) with a core of SiO2(CHA) / Al2O3(cHA) ratio between 8 and 20 - and also the layer zeolite with a SiO2 (cha / A12O3 (CHa) ratio between 160 and 200. Preferably, the X-ray diffraction pattern does not contain any other lines of significant intensity (i.e., intensity greater than about three times the background noise) than those present in the core zeolite.

[0070] Core-layer zeolite obtained: IZM-11 zeolitic material obtained

[0071] The core-layer zeolite obtained (IZM-11 material) of CHA structural type, when calcined, is generally analyzed by X-ray diffraction, this technique also making it possible to determine the purity of said zeolite obtained by the process of the invention.

[0072] Very advantageously, the process of the invention leads to the formation of an IZM-11 zeolite of CHA structural type, free from any other crystallized or amorphous phase, advantageously of a purity greater than or equal to 97%, preferably greater than or equal to 98%, very preferably greater than or equal to 99%. The zeolite material obtained has a core SiO2 / Al2O3 ratio of between 8 and 30, preferably between 10 and 14, for a layer SiO2 / Al2O3 ratio of between 160 and purely silicic, preferably between 200 and 800, more preferably between 200 and 300.

[0073] The loss on ignition of the IZM-11 zeolite of CHA structural type obtained after drying and before calcination is generally between 6 and 20% by weight.

[0074] According to the invention, loss on ignition (LOI) is understood to mean the percentage loss of mass undergone by a solid compound, a mixture of solid compounds or a paste - in the present case, it is the IZM-11 zeolite of CHA structural type prepared according to the invention at the end of step v) - during a heat treatment at 1000°C for 2 hours, in a static furnace (muffle furnace type), relative to the mass of the initial solid compound, mixture of solid compounds or paste - in the present case of the present invention relative to the mass of dried IZM-11 zeolite of CHA structural type tested at the end of step v). Loss on ignition generally corresponds to the loss of solvent (such as water) contained in solids, but also to the elimination of organic compounds contained in mineral solid constituents. Characterization techniques

[0075] The X-ray diffraction pattern is obtained by radiocrystallographic analysis using a diffractometer using the classical powder method with Ka radiation, copper (X = 1.5406Â). From the position of the diffraction peaks represented by the angle 20, the characteristic reticular equidistances dhki of the sample are calculated using the Bragg relation. The measurement error A(dhki) on dhki 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 in Angstroms (Â). Each of these values ​​must be assigned the measurement error A(dhki) between ± 0.6Â and ± 0.01Â.

[0076] X-ray fluorescence (FX) 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.

[0077] Inductively coupled plasma optical emission spectroscopy (ICP-OES) is an analytical technique that allows the determination of chemical elements (except hydrogen, nitrogen, carbon, oxygen and halogens). The sample is ionized by injection into a high-temperature plasma. The electrons of the ionized atoms emit a characteristic photon, analyzed by one or more monochromators.

[0078] Scanning electron microscopy (SEM) is an analytical technique that produces images of the surface of a sample using electron-matter interactions.

[0079] Energy dispersive X-ray spectroscopy (EDX) is an analytical technique coupled with the scanning transmission electron microscope (STE) which uses the excitation of matter by X-rays. It allows the analysis of chemical elements within the detection limit of 0.1% in concentration.

[0080] The layer thickness, core diameter and growth percentage are defined by this analysis, considering the core zeolite and the Si / Al gradient core-layer zeolite as spherical particles.

[0081] The ratios of the SARs of the core and the layer make it possible to define a magnitude of difference of the SARs: ASAR=SARlayer / SARcore

[0082] The water adsorption isotherm is an analytical technique that allows the amount of water adsorbed on a material in a known atmosphere to be related to the water pressure applied to the material. Here, the amount of water adsorbed on the material is given at a temperature of 25°C and a pressure of 0.95 bar (0.9 x 105Pa): If the amount of water adsorbed is less, then the material is relatively more hydrophobic. Applications

[0083] The IZM-11 zeolite of CHA core-layer structural type with Si / Al gradient obtained by the process of the invention, with the characteristics of the invention can be used directly or after calcination as an acid solid for catalysis in the fields of refining and petrochemistry or in the field of pollution control, in particular automotive (treatment of NOx in particular by catalytic reduction type SCR, an acronym for Selective Catalytic Reduction or selective catalytic reduction in French). It can also be used as an adsorbent or as a molecular sieve. EXAMPLES

[0084] The invention is illustrated by the following examples which are in no way limiting.

[0085] Example 1: preparation of an IZM-11 core-layer zeolite with Si / Al gradient of CHA structural type according to the invention with a SiO2 / zeolite (powder) mass ratio = 0.95

[0086] 0.06 g of aluminum hydroxide (58.55% by weight of Al2O3) was mixed with 0.44 g of sodium hydroxide, 8.92 g of N,N,N-trimethyl-l-adamantamonium (20.11% by weight) and 54.5 g of ultrapure water. The mixture obtained is kept stirring for 4

[0087] hours. 11.07 g of LUDOX-HS40 (40% by weight of SiO2) are added dropwise to the mixture. The mixture obtained is kept stirring for 4 hours. The molar composition of the precursor gel obtained is as follows: 10 SiO2: 0.05 Al2O3: 0.96 Na2O: 1.15 R: 514 H2O. 4.66 g of zeolite (here SSZ-13) of structural type CHA (SiO2 / Al2O3= 10.8) are added to the mixture and kept stirring until a homogeneous suspension is obtained. The gel obtained is transferred to an autoclave. The autoclave is closed and then heated for 96 hours at 160°C with stirring at 20 rpm with a rotisserie system. The solid obtained is filtered, washed with deionized water and then dried overnight at 100°C.The solid is then introduced into a muffle furnace where a calcination step is carried out: 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 550°C followed by a hold at 550°C maintained for 8 hours and then a return to room temperature.

[0088] The calcined solid product was analyzed by X-ray diffraction and identified as consisting of an IZM-11 zeolite of CHA structural type with a purity greater than 99% by weight.

[0089] X-ray fluorescence analysis gives a molar ratio SiO2 / Al2O3 = 20.8 and ICP-OES analysis gives a molar ratio Al2O3 / Na2O = 1.75.

[0090] METB-EDX analysis gives a molar ratio of the layer zeolite SiO2 / A12O3 = 208.

[0091] We thus obtain a material with a difference in SAR between the core and the ASAr layer equal to 19.3.

[0092] The thickness of the layer CHA structural type zeolite is 43 nm and the core CHA structural type zeolite is 263 nm, i.e. a growth percentage of 33% measured by STEM-EDX.

[0093] Example 2: preparation of an IZM-11 core-layer zeolite with Si / Al gradient of CHA structural type according to the invention with a SiO2 / zeolite (powder) mass ratio = 0.55

[0094] 0.06 g of aluminum hydroxide (58.55% by weight of Al2O3) was mixed with 0.44 g of sodium hydroxide, 8.92 g of N,N,N-trimethyl-l-adamantamonium (20.11% by weight) and 54.5 g of ultrapure water. The mixture obtained is kept stirring for 4 hours. 11.07 g of LUDOX-HS40 (40% by weight of SiO2) are added dropwise to the mixture. The mixture obtained is kept stirring for 4 hours. The molar composition of the precursor gel obtained is as follows: 10 SiO2: 0.05 A12O3: 0.96 Na2O: 1.15 R: 514 H2O. 8.15 g of zeolite (here SSZ-13) of structural type CHA (SiO2 / A12O3 = 10.8) are added to the mixture and kept stirring until a homogeneous suspension is obtained. The gel obtained is transferred to an autoclave. The autoclave is closed and then heated for 96 hours at 160°C with stirring at 20 rpm using a rotisserie system. The solid obtained is filtered, washed with deionized water and then dried overnight at 100°C.The solid is then introduced into a muffle furnace where a calcination step is carried out: 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 550°C followed by a hold at 550°C maintained for 8 hours and then a return to room temperature.

[0095] The calcined solid product was analyzed by X-ray diffraction and identified as consisting of an IZM-11 zeolite of CHA structural type with a purity greater than 99% by weight.

[0096] X-ray fluorescence analysis gives a molar ratio SiO2 / Al2O3 = 19.2 and ICP-OES analysis gives a molar ratio Al2O3 / Na2O = 3.4.

[0097] METB-EDX analysis gives a molar ratio of the layer zeolite SiO2 / A12O3 = 200, which results in Asar equal to 18.5.

[0098] The thickness of the layer CHA structural type zeolite is 20 nm and the core CHA structural type zeolite is 230 nm, i.e. a growth percentage of 17% measured by STEM-EDX.

[0099] Example 3: preparation of an IZM-11 core-layer zeolite with Si / Al gradient of CHA structural type according to the invention with a SiO2 / zeolite (powder) mass ratio = 7

[0100] 0.06 g of aluminum hydroxide (58.55% by weight of Al2O3) was mixed with 0.44 g of sodium hydroxide, 8.92 g of N,N,N-trimethyl-l-adamantamonium (20.11% by weight) and 54.5 g of ultrapure water. The mixture obtained is kept stirring for 4 hours. 11.07 g of LUDOX-HS40 (40% by weight of SiO2) are added dropwise to the mixture. The mixture obtained is kept stirring for 4 hours. The molar composition of the precursor gel obtained is as follows: 10 SiO2: 0.05 A12O3: 0.96 Na2O: 1.15 R: 514 H2O. 0.63 g of zeolite (SSZ-13) of structural type CHA (SiO2 / Al2 O3= 10.8) are added to the mixture and kept stirring until a homogeneous suspension is obtained. The gel obtained is transferred to an autoclave. The autoclave is closed and then heated for 96 hours at 160°C with stirring at 20 rpm using a rotary spit system. The solid obtained is filtered, washed with deionized water and then dried overnight at 100°C.The solid is then introduced into a muffle furnace where a calcination step is carried out: 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 550°C followed by a hold at 550°C maintained for 8 hours and then a return to room temperature.

[0101] The calcined solid product was analyzed by X-ray diffraction and identified as consisting of an IZM-11 zeolite of CHA structural type with a purity greater than 99% by weight.

[0102] X-ray fluorescence analysis gives a molar ratio SiO2 / Al2O3 = 85 and ICP-OES analysis a molar ratio Al2O3 / Na2O = 1.85.

[0103] The METB-EDX analysis gives a molar ratio of the layer zeolite SiO2 / A12O3 = 160, which results in an ASARequal to 14.8.

[0104] The thickness of the layer CHA structural type zeolite is 244 nm and that of the core CHA structural type zeolite is 314 nm, i.e. a growth percentage of 155% measured by STEM-EDX.

[0105] Example 4: preparation of an IZM-11 core-layer zeolite with Si / Al gradient of CHA structural type in a purely silicic medium with a SiO2 / zeolite (powder) mass ratio = 0.95

[0106] 0.44 g of sodium hydroxide was mixed with 8.92 g of N,N,N-trimethyl-l-adamantamonium (20.11% by weight) and 54.5 g of ultrapure water. The resulting mixture is stirred for 4 hours. 11.07 g of LUDOX- HS40 (40% by weight of SiO2) are added dropwise to the mixture. The mixture obtained is kept stirring for 4 hours. The molar composition of the precursor gel obtained is as follows: 10 SiO2 : 0.96 Na2O : 1.15 R : 514 H2O. 4.66 g of zeolite (for example SSZ-13) of structural type CHA (SiO2 / Al2O3= 10.8) are added to the mixture and kept stirring until a homogeneous suspension is obtained. The gel obtained is transferred to an autoclave. The autoclave is closed and then heated for 96 hours at 160°C while stirring at 20 rpm with a rotisserie system. The solid obtained is filtered, washed with deionized water and then dried overnight at 100°C.The solid is then introduced into a muffle furnace where a calcination step is carried out: 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 550°C followed by a hold at 550°C maintained for 8 hours and then a return to room temperature.

[0107] The calcined solid product was analyzed by X-ray diffraction and identified as consisting of an IZM-11 zeolite of CHA structural type with a purity greater than 98% by weight.

[0108] X-ray fluorescence analysis gives a molar ratio SiO2 / Al2O3 = 26.1 and ICP-OES analysis a molar ratio Al2O3 / Na2O = 1.45.

[0109] The METB-EDX analysis gives a molar ratio of the SiO2 / A12O3 layer zeolite ~ 700, at the limit of detection of the device, indicating a layer close to purely silicic. This results in an ASAr of approximately 65.

[0110] The thickness of the layer CHA structural type zeolite is 18nm and the core CHA structural type zeolite is 158nm, i.e. a growth percentage of 23% measured by STEM-EDX.

[0111] Example 5: preparation of an IZM-11 core-layer zeolite with Si / Al gradient (core SAR=20) of CHA structural type in a purely silicic medium with a mass ratio SiO2 / (zeolite powder)= 0.55

[0112] 0.44 g of sodium hydroxide was mixed with 8.92 g of N,N,N-trimethyl-l-adamantamonium (20.11% by weight) and 54.5 g of ultrapure water. The mixture obtained is kept stirring for 4 hours. 11.07 g of LUDOX-HS40 (40% by weight of SiO2) are added dropwise to the mixture. The mixture obtained is kept stirring for 4 hours. The molar composition of the precursor gel obtained is as follows: 10 SiO2: 0.96 Na2O: 1.15 R: 514 H2O. 4.66 g of zeolite SSZ-13 of structural type CHA (SiO2 / Al2O3= 20.4) are added to the mixture and kept stirring until a homogeneous suspension is obtained. The gel obtained is transferred to an autoclave. The autoclave is closed and then heated for 96 hours at 160°C with stirring at 20 rpm using a rotisserie system. The solid obtained is filtered, washed with deionized water and then dried overnight at 100°C. The solid is then introduced into a muffle furnace where a calcination step is carried out: 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 550°C followed by a hold at 550°C maintained for 8 hours and then a return to room temperature.

[0113] The calcined solid product was analyzed by X-ray diffraction and identified as consisting of an IZM-11 zeolite of CHA structural type with a purity greater than 99% by weight.

[0114] .The METB-EDX analysis gives a molar ratio of the layer zeolite SiO2 / A12O3 = 216., which results in an ASAr of 0.6.

[0115] The thickness of the layer CHA structural type zeolite is 23 nm and the core CHA structural type zeolite is 197 nm, i.e. a growth percentage of 23% measured by STEM-EDX.

[0116] Example 6: Comparative water adsorption isotherm measurement, on the one hand on a SSZ-13 zeolite of CHA structural type with SAR=10.8, and on the other hand on the IZM-11 zeolitic material described in example 3

[0117] At a pressure of 0.95 bar, the quantity of water vapor adsorbed on the SSZ-13 zeolite of CHA type of SAR = 10.8 is 348 cmVg, or 20.5% by mass.

[0118] At a pressure of 0.95 bar, the quantity of water vapor adsorbed on the IZM-11 in accordance with the invention and described in Example 3 is 280 cmVg, or 16.5% by mass.

[0119] We therefore verify that IZM-11 has a more hydrophobic character than its core alone, with 4% less water by mass adsorbed, which makes in percentage almost 20% less water adsorbed by mass in the layer.

[0120] This characteristic can prove to be very advantageous, in particular, as mentioned above, when this material is intended to be used as a catalyst, in particular as an SCR type decontamination catalyst, the water adsorbed on the surface of the catalyst grains being able to at least partially deactivate its active sites and therefore reduce its reactivity.

Claims

Claims

1. A method for preparing a zeolitic material of the IZM-11 core-layer zeolite type with a Si / Al gradient of the CHA structural type comprising at least the following steps: i) the mixture in an aqueous medium of a source of silicon, a source of aluminum, an organic nitrogen compound R, R being N,N,N-trimethyl-1-adamantamonium, and sodium hydroxide, the reaction mixture having the following molar composition: H2O / SiO2 between 40 and 100, preferably between 40 and 60 SiO2 / Al2O3 between 160 and infinity, preferably between 180 and 240 SiO2 / R between 5 to 20, preferably between 7 and 10 SiO2 / Na2O between 5 and 50, preferably between 8 and 15 in which Na2O denotes the quantity of Na2O provided by the sodium hydroxide, SiO2 denotes the quantity of SiO2 provided by the source of silicon, and Al 2O3 denotes the quantity of Al2O3 provided by the source of aluminum, up to obtaining a homogeneous precursor gel; ii) the addition of a zeolite in powder form, of CHA structural type with a SiO2 / Al2O3 SAR molar ratio of between 8 and 30, preferably between 10 and 14, until a homogeneous suspension is obtained, with a SiO2 / zeolite mass ratio of between 0.2 and 11, preferably between 0.5 and 7 iii) the hydrothermal treatment of said precursor gel obtained at the end of step ii) at a temperature between 130°C and 180°C, for a period between 2 hours and 8 days until a core-layer zeolite with a Si / Al gradient IZM-11 of CHA structural type is obtained with a molar ratio value SiO2 / Al2O3 - less than or equal to 30, in particular between 8 and 30, for the heart - and at least 160, in particular at least 180 or at least 200 for the layer. iv) Washing the gel obtained at the end of step iii) with distilled water until a solution is obtained after washing with a pH between 7 and 8 v) Drying the wet solid obtained from step iv) for a period of between 4 hours and 24 hours at a temperature of between 20 and 150°C. vi) Optional calcination of the dried solid obtained at the end of step v), in particular at a temperature between 420°C and 600°C for a period of between 6 hours and 16 hours, the calcination possibly being preceded by a gradual increase in temperature.

2. Process for preparing the zeolitic material according to the preceding claim, in which the overall SiO2 / Al2O3 molar ratio of the IZM-11 zeolite of CHA structural type obtained is between 16 and 120, preferably between 20 and 85.

3. Process for preparing the zeolitic material according to one of the preceding claims, in which step i) comprises a step of maturing the reaction mixture at a temperature of between 15 and 35°C, with stirring, for a period of between 2 hours and 8 hours, preferably between 3 hours and 5 hours.

4. Process for preparing the zeolitic material according to one of the preceding claims, in which the zeolite of CHA structural type added in powder form to the reaction medium in step ii) has a particle size of between 50 nm and 10 qm, preferably between 100 nm and 3 qm.

5. Process for preparing the zeolitic material according to one of the preceding claims, in which the hydrothermal treatment of step iii) is carried out under autogenous pressure at a temperature of between 150°C and 165°C, for a period of between 2 days and 7 days, and preferably between 4 days and 6 days.

6. Process for preparing the zeolite material according to one of the preceding claims, in which the solid phase obtained at the end of step iii) is filtered, washed, and dried at a temperature between 60 and 100°C, for a period between 4 hours and 24 hours to obtain a dried zeolite.

7. Zeolitic material of the IZM-11 core-layer zeolite type of CHA structural type with Si / Al gradient, in particular obtained by the preparation process according to one of the preceding claims, in which - the SiO2 / Al2O3 molar ratio of the core is between 8 and 30, - the SiO2 / Al2O3 molar ratio of the layer is at least between 160 - and in which the layer has a thickness of between 10% and 200% growth percentage, preferably between 20% and 150% growth percentage.

8. Composite zeolite material of IZM-11 core-layer zeolite type of CHA structural type with Si / Al gradient according to the preceding claim, in which the SiO2 / Al2O3 molar ratio of the layer is

9.

10.

11.

12. infinite, the layer being purely silicic. Composite zeolite material of the IZM-11 core-layer zeolite type of CH A structural type with Si / Al gradient according to claim 7, in which the SiO2 / Al2O3 molar ratio of the layer is at least 200, and preferably at most 800 or at most 300. Composite zeolite material of the IZM-11 core-layer zeolite type of CHA structural type with Si / Al gradient according to one of claims 7 to 9, in which the SiO2 / Al2O3 molar ratio of the core is at most 20, and is in particular between 10 and 14. Composite zeolite material of the IZM-11 core-layer zeolite type of CHA structural type with Si / Al gradient according to one of claims 7 to 10, in which the ASAr ratio of the SiO2 / Al2O3 molar ratio of the layer to the SiO2 / Al2O3 molar ratio of the core is at least 10, in particular at least 20 or at least 50, or at least 70 or at least 80. Composite zeolite material of the IZM-11 core-layer zeolite type of CHA structural type with Si / Al gradient according to one of claims 7 to 11, comprising at least the following X-ray diffraction lines: 2 theta (°) Irel 2 theta (°) Irel 9.598 FF 26.225 f 13.055 mf 27.877 ff 14.144 ff 28.345 ff 16.217 f 29.973 ff 17.977 f 30.89 mf 19.299 ff 31.096 mf 20.797 m 31.324 mf 22.232 ff 32.782 ff 22.762 ff 33.819 ff 23.269 ff 34.833 ff 25.243 f 36.393 ff where FF = very strong; F = strong; m = medium; mf = medium weak; f = weak; ff = very weak. The relative intensity Irei is given in relation to a relative intensity scale where a value of 100 is assigned to the strongest line intense X-ray diffraction pattern: ff <15; 15 <f <30 ; 30 < mf <50 ; 50 <m<65 ; 65 <F<85 ; FF > 85.

13. Composite zeolite material of the IZM-11 core-layer zeolite type of CHA structural type with Si / Al ratio gradient according to one of claims 7 to 12, with a purity greater than or equal to 97%.

14. Composite zeolite material of the IZM-11 core-layer zeolite type of CHA structural type with Si / Al ratio gradient according to one of claims 7 to 13, in which the layer has a more hydrophobic character than the core.

15. Application of the composite zeolite material of the core-layer zeolite type IZM-11 of CHA structural type with Si / Al ratio gradient according to one of claims 7 to 14 as a catalyst, molecular sieve or adsorbent.

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