WO2019224089A1

WO2019224089A1 - Catalyst containing an aluminosilicate composite material comprising copper and a mixture of afx- and bea-structure zeolites, for selective reduction of nox

Info

Publication number: WO2019224089A1
Application number: PCT/EP2019/062561
Authority: WO
Inventors: David BERTHOUT; Bogdan Harbuzaru
Original assignee: IFP Energies Nouvelles
Priority date: 2018-05-24
Filing date: 2019-05-16
Publication date: 2019-11-28
Also published as: FR3081338B1; FR3081338A1

Abstract

The invention relates to a catalyst comprising a zeolite composite material, consisting of a mixture of AFX- and BEA-structure zeolites, also containing copper and, optionally, at least one additional transition metal, the preparation method thereof, and the use of same for the selective catalytic reduction of NOx in the presence of a reducing agent such as NH₃ or H₂.

Description

CATALYST BASED ON A COMPOSITE ALUMINOSILICATE MATERIAL COMPRISING COPPER AND A MIXTURE OF STRUCTURAL TYPE AFX AND BEA STRUCTURAL TYPE ZEOLITES FOR THE SELECTIVE REDUCTION OF NOx

TECHNICAL FIELD OF THE INVENTION

The subject of the invention is a catalyst based on a composite aluminosilicate material comprising a mixture of a zeolite of structural type AFX and a zeolite of structural type BEA, and containing copper, said catalyst possibly comprising a transition metal. its method of preparation and its use for selective catalytic reduction of NOx in the presence of a reducing agent, in particular on internal combustion engines.

PRIOR ART

The emissions of nitrogen oxides (NOx) that result from the burning of fossil fuels are a major concern for society. Increasingly stringent standards are being put in place by government authorities to limit the impact of emissions from combustion on the environment and on health. For light vehicles in Europe under the Euro 6c regulation, NOx and particulate emissions must reach a very low level for all operating conditions. The new Worldwide Harmonized Light Vehicles Test Cycle (WLTC) and compliance-related real-driving emissions (RDE) require the development of a highly effective pollution control system to achieve these objectives. The selective catalytic reduction, designated by the acronym "SCR" for "Selective Catalytic Reduction", appears as an efficient technology to eliminate nitrogen oxides in the oxygen-rich exhaust gas, typical of diesel engines and with positive ignition in lean mixture. The selective catalytic reduction is achieved by a reducing agent, generally ammonia, and can thus be designated NH ₃ -SCR. The ammonia (NH ₃ ) involved in the SCR process is generally generated via the decomposition of an aqueous urea solution (AdBlue or DEF), and produces N ₂ and H ₂ O during the reaction with NOx.

Zeolites exchanged with transition metals are used in particular as catalysts for NH ₃ -SCR applications in transport. Small-pore zeolites, particularly copper-exchanged chabazites, are particularly suitable. They commercially exist in the form of Cu-SAPO-34 silico-aluminophosphate and Cu-SSZ-13 (or Cu-SSZ-62) aluminosilicates. Their hydrothermal behavior and their NOx conversion efficiency make them the current references. However, the standards being more and more constraining, the performance of the catalysts still needs to be improved.

The use of zeolites AFX structural type for NH ₃ -SCR applications is known, but few studies evaluate the effectiveness of catalysts implementing this zeolite.

Fickel et al. (Fickel, DW, & Lobo, RF (2009), The Journal of Physical Chemistry C, 14 (3), 1633-1640) studies the use of a copper-exchanged SSZ-16 (structural type AFX) for elimination of NOx. This zeolite is synthesized according to US Pat. No. 5,194,235, wherein the copper is introduced by exchange using copper (II) sulfate at 80 ° C for 1 h. Recent results (Fickel, DW, D'Addio, E., Lauterbach, JA, & Lobo, RF (201 1), 102 (3), 441-448) show excellent conversion and good hydrothermal stability for 3.78% copper weight.

Work on the synthesis of AFX structural zeolites has been carried out with various structural agents (Lobo, RF, Zones, SI, & Medrud, RC (1996), Chemistry of Materials, 8 (10), 2409-241 1) and that optimization works of synthesis (Hrabanek, P., Zikanova, A., Supinkova, T., Drahokoupil, J., Fila, V., Lhotka, M., Bernauer, B. (2016), Microporous and Mesoporous Materials, 228, 107-115).

Wang et al. (Wang, D. et al., CrystEngComm., (2016), 18 (6), 1000-1008) studied the replacement of the TMHD structuring agent with a TEA-TMA mixture for the formation of SAPO-56 and obtained unwanted phases SAPO-34 and SAPO-20. The incorporation of transition metals is not discussed.

The application US 2016/0137518 describes a quasi-pure zeolite AFX, its synthesis from sources of silica and alumina in the presence of a structuring agent of type 1, 3-Bis (1-adamantyl) imidazolium hydroxide, the preparation a transition metal-exchanged zeolite AFX catalyst and its use for NH ₃ -SCR applications. No particular form of AFX zeolite is mentioned.

More recently, application US 2018/0093259 discloses the synthesis of zeolites with small pores, such as the zeolite of the structural type AFX, from zeolite of FAU type in the presence of a structurant, such as 1,3-bis (1 - adamantyl) imidazolium hydroxide and an alkaline earth metal source. It also presents applications of the zeolite of AFX structural type obtained, in particular the use of this zeolite as NOx reduction catalyst, after exchange with a metal such as iron. Meanwhile, the application US 2016/0096169A1 discloses the use in the NOx conversion of a catalyst based on a zeolite AFX structural type having a Si / Al ratio of 15 to 50 exchanged with a metal, the zeolite AFX being obtained from a structuring agent of type 1, 3-Bis (1-adamantyl) imidazolium hydroxide. The results obtained, in the conversion of NOx, show in particular a selectivity of the catalysts prepared according to US 2018/0093259 and US 2016/0096169 to nitrous oxide not exceeding 20 ppm.

JP 2014-148441 describes the synthesis of a solid related to an AFX zeolite, in particular an SAPO-56 comprising copper usable for the reduction of NO _x . The solid is synthesized and then added to a mixture comprising an alcohol and a copper salt, the whole being calcined. The copper is therefore added after the formation of the SAPO solid which is related to the AFX structural type zeolite. This traded solid appears to have increased resistance to the presence of water.

Ogura et al. (Bull Chemical Co., 2018, 91, 355-361) show the very good activity of a copper-exchanged zeolite SSZ-16 relative to other zeolite structures, even after hydrothermal aging.

WO 2017/080722 discloses a direct synthesis of a zeolite containing copper. This synthesis requires starting from a zeolite of structural type FAU and using a complexing agent TEPA and an element M (OH) _x to result in different types of zeolites, mainly of type CHA. Zeolites of the ANA, ABW, PHI and GME type are also produced.

The Applicant has discovered that a catalyst comprising a copper-containing composite aluminosilicate material and a mixture of an AFX structural type zeolite and a BEA structural type zeolite, and optionally comprising an additional transition metal, in particular copper , has interesting performance of NO _x conversion and selectivity towards N ₂ 0. The NOx conversion performances, in particular at low temperature (T <250 ° C.), are in particular greater than those obtained with catalysts of the prior art, such as catalysts based zeolite AFX structural type copper-exchanged, while maintaining a good selectivity to nitrous oxide N ₂ 0. OBJECT AND INTEREST OF THE INVENTION

The present invention relates to a process for the preparation of a catalyst comprising a zeolite composite material composed of a mixture of zeolites of structural type AFX and of structural type BEA and containing copper, comprising at least the following stages: i) mixing into aqueous medium, at least one zeolite with structure type FAU having a molar ratio Si0 ₂ (FAU) / AI ₂ 0 ₃ (FAU) between 2 and 200, at least one organic nitrogen compound selected from R dihydroxide 1, 5-bis (methylpiperidinium) pentane, 1,6-bis (methylpiperidinium) hexane dihydroxide, 1,7-bis (methylpiperidinium) heptane dihydroxide and mixtures thereof, at least one source of at least one alkali metal and / or alkaline earth metal M of valence n, n being an integer greater than or equal to 1, at least one organic complexing agent and at least one copper source, to obtain a precursor gel, the mixture reaction having the following molar composition:

(SiO ₂ (FAU)) / (Al ₂ O ₃ (FAU)) from 2 to 200;

H ₂ 0 / (Si0 ₂ (FAU>) of from 1 to 100;

R / (Si0 ₂ (FAU)) of from 0.01 to 0.6;

M ₂ / n 0 / (Sl0 ₂ (FAU)) of 0.005 to 0.7;

CuO / (SiO _{2 (FAU)} ) between 0.005 to 0.06;

OCPLX / CuO between 0.8 to 2;

wherein Si0 _{2 (F} AU) refers to the molar amount of SiO ₂ provided by the FAU zeolite, and Al ₂ 0 _{3 (FAU)} refers to the molar amount of Al ₂ O ₃ provided by the FAU zeolite, H ₂ 0 the molar amount of water present in the reaction mixture, R the molar amount of said nitrogenous organic compound, M _{2 / n} O being the molar amount of M _{2 / n} O provided by the FAU zeolite and the source of the alkali metal and / or metal alkaline earth, OCPLX is the molar amount of organic complexing agent and CuO is the molar amount of CuO supplied by the copper source;

ii) the hydrothermal treatment of said precursor gel obtained at the end of step i) at a temperature of between 120 ° C. and 220 ° C., for a period of between 12 hours and 15 days, in order to obtain a crystallized solid phase, called "solid";

iii) optionally at least one ion exchange comprising contacting the solid obtained at the end of the preceding step, with at least one solution comprising at least a species capable of releasing a transition metal in solution in reactive form with stirring at ambient temperature for a period of between 1 hour and 2 days; iv) the heat treatment by drying of the solid obtained at the end of the preceding step at a temperature of between 20 and 150 ° C. for a duration of between 2 and 24 hours, followed by calcination under an air stream; at a temperature between 450 and 700 ° C for a period of between 2 and 20 hours.

The present invention also relates to a catalyst comprising a composite material comprising a mixture of an AFX zeolite and a BEA-type zeolite, and containing copper, at a content of between 0.05 and 6% by weight, preferably between 0.5 and 5 wt%, and more preferably between 1 and 4 wt%, relative to the total weight of said catalyst in its anhydrous form, said catalyst having a zeolitic structure comprising:

between 30 and 90% by weight, preferably between 40 and 80% by weight of zeolite of structural type AFX, relative to the total weight of said catalyst in its anhydrous form;

between 10 and 70% by weight, preferably between 20 and 60% by weight of zeolite of structural type BEA, relative to the total mass of said catalyst in its anhydrous form;

said catalyst optionally further comprising at least one additional transition metal selected from the group consisting of: Ti, V, Mn, Mo, Fe, Co, Cu, Cr, Zn, Nb, Ce, Zr, Rh, Pd, Pt, Au, W, Ag, preferably Cu, Fe, Nb, Ce, Mn, the total content of transition metal being between 0.5 and 6% by weight, preferably between 0.5 and 5% by weight, and even more preferably between 1 and 4% by weight, based on the total mass of the final catalyst, in its anhydrous form.

The present invention also relates to the use of the preceding catalyst or prepared by the method described above for the selective catalytic reduction of NOx by a reducing agent such as NH ₃ or H ₂ .

The interest of the present invention lies in the particular catalyst, based on a composite microporous aluminosilicate material containing an intimate mixture of a zeolite of structural type AFX and a zeolite of BEA structural type, and a transition metal, in particular copper, advantageously prepared by the process according to the invention. The catalyst according to the invention has in fact improved properties compared to the catalysts of the prior art. In particular, the use of the catalyst according to the invention or prepared according to the process of the invention makes it possible to obtain lower priming temperatures for the NOx conversion reaction and a better conversion of NO _x on the whole. operating temperature range (150 ° C - 600 ° C), while maintaining a good N ₂ 0 selectivity.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates, in particular, to a process for the preparation of a catalyst comprising a zeolite composite material composed of a mixture of zeolites of structural type AFX and of structural type BEA and containing copper, comprising at least, preferably consisting of , the following steps:

i) mixing in an aqueous medium, at least one zeolite of structural type FAU having a molar ratio SiO _{2 (FAU)} / Al ₂ O _{3 (FAU)} of between 2 and 200, of at least one nitrogenous organic compound R selected from 1,5-bis (methylpiperidinium) pentane dihydroxide, 1,6-bis (methylpiperidinium) hexane dihydroxide, 1,7-bis (methylpiperidinium) heptane dihydroxide and mixtures thereof, from at least one source at least one alkali metal and / or alkaline earth metal M of valence n, n being an integer greater than or equal to 1, at least one organic complexing agent and at least one copper source, to obtain a precursor gel, the reaction mixture having the following molar composition:

(Si0 ₂ (FAU)) / (AI ₂ 0 ₃ (FAU>) of from 2 to 200;

H ₂ 0 / (Si0 ₂ (FAU>) of from 1 to 100;

R / (Si0 _{2 (FAU)} ) of from 0.01 to 0.6;

M _{2 / n} 0 / (Sl0 ₂ (FAU)) of 0.005 to 0.7;

CuO / (SiO _{2 (FAU)} ) between 0.005 to 0.06;

OCPLX / CuO between 0.8 to 2;

wherein Si0 _{2 (F} AU) refers to the molar amount of SiO ₂ provided by the FAU zeolite, and Al ₂ 0 _{3 (FAU)} refers to the molar amount of Al ₂ O ₃ provided by the FAU zeolite, H ₂ 0 the molar amount of water present in the reaction mixture, R the molar amount of said nitrogenous organic compound, M _{2 / n} O being the molar amount of M _{2 / n} O provided by the FAU zeolite and the source of the alkali metal and / or metal alkaline earth, OCPLX is the quantity molar organic complexing agent and CuO is the molar amount of CuO provided by the copper source;

iii) optionally at least one ion exchange comprising contacting the solid obtained at the end of the preceding step with at least one solution comprising at least one species capable of releasing a transition metal, in particular copper, in solution in reactive form with stirring at ambient temperature for a period of between 1 h and 2 d;

iv) the heat treatment by drying of the solid obtained at the end of the preceding step at a temperature of between 20 and 150 ° C. for a duration of between 2 and 24 hours, followed by calcination under an air stream; at a temperature between 450 and 700 ° C for a period of between 2 and 20 hours; steps iii) and iv) can advantageously be inverted, and possibly repeated if necessary.

Preferably, the preparation process according to the invention comprises step i) of mixing, step ii) of hydrothermal treatment, step iii) of ionic exchange and step iv) of heat treatment, the steps iii) and iv) can advantageously be inverted, and possibly repeated if necessary.

According to the invention, the terms "gel" and "precursor gel" are synonymous and correspond to the homogeneous reaction mixture obtained at the end of step i) of the process according to the invention.

According to the present invention, the expression "between ... and ..." means that the values across the range are included in the range of values described. If this were not the case and the terminal values were not included in the range described, such precision will be provided by the present description of the invention.

The invention also relates to the catalyst itself, composed of a mixture of zeolites of structural type AFX and of structural type BEA and containing copper, and optionally comprising an additional transition metal, said catalyst being advantageously capable of being obtained or obtained directly by the preparation process of the invention. The invention also relates to the use of a catalyst according to the invention or prepared by a process according to the invention for the selective catalytic reduction of NOx in the presence of a reducing agent.

The catalyst

The catalyst comprises at least one composite material comprising a mixture of an AFX zeolite and a BEA-type zeolite, and containing copper, said catalyst optionally further comprising at least one additional transition metal. Said additional transition metal optionally contained in the catalyst is selected from the group consisting of the following elements: Ti, V, Mn, Mo, Fe, Co, Cu, Cr, Zn, Nb, Ce, Zr, Rh, Pd, Pt, Au, W, Ag, preferably Cu, Fe, Nb, Ce, Mn. The total content of the transition metal catalyst, taking into account the amount of copper of the composite material of said catalyst, is between 0.5 and 6 wt.%, Preferably between 0.5 and 5 wt. more preferred between 1 and 4% by weight, based on the total mass of the final catalyst, in its anhydrous form.

The catalyst according to the invention has a zeolite structure comprising:

between 10 and 70% by weight, preferably between 20 and 60% by weight of zeolite of structural type BEA, relative to the total mass of said catalyst in its anhydrous form.

The catalyst according to the invention comprises between 0.05 and 6% by weight, preferably between 0.5 and 5% by mass and more preferably between 1 and 4% by weight of copper element, with respect to the total mass of said catalyst under its purity. anhydrous form.

Preferably, the weight ratio (AFX / BEA) of the AFX zeolite relative to the BEA zeolite in the catalyst according to the invention is between 0.4 and 9, preferably between 0.5 and 7.5 and more. preferably still between 1 and 4. Advantageously, the zeolite of structural type BEA of the catalyst according to the invention is preferably a zeolite beta containing a mixture containing between 35 and 45% by weight, preferably 40% by mass, of polymorph A and between and 65% by weight, preferably 60% by mass, of polymorph B. The catalyst according to the invention advantageously has a molar ratio Si0 ₂ / Al ₂ 0 ₃ between 2 and 100, preferably between 4 and 90 and more preferably between 6 and 80.

Advantageously, the catalyst defined above can be obtained or is obtained directly by the preparation process according to the invention.

According to the invention, the terms "composite material", "zeolite composite material" and "composite aluminosilicate material" are synonymous and used interchangeably to designate a solid material composed of a mixture of zeolites of structural type AFX and of structural type BEA and containing copper. The composite material of the catalyst according to the invention comprising an intimate zeolite mixture of AFX type and a BEA-type zeolite is advantageously prepared by direct synthesis, that is to say in a single reaction step. The composite material is the solid advantageously obtained at the end of the hydrothermal treatment step ii) of the process for preparing the catalyst according to the invention. The composite aluminosilicate material, containing copper and an intimate mixture of zeolites AFX and BEA, does not result from a simple mechanical mixing of at least one zeolite of structural type AFX and at least one zeolite of structural type BEA.

According to the invention, the additional transition metal optionally included in the catalyst is selected from the group consisting of the elements of groups 3 to 12 of the periodic table of the elements including the lanthanides. In particular, the transition metal is selected from the group consisting of: Ti, V, Mn, Mo, Fe, Co, Cu, Cr, Zn, Nb, Ce, Zr, Rh, Pd, Pt, Au, W , Ag. Preferably, it comprises copper, alone or in combination with at least one other transition metal, selected from the group of elements previously listed, in particular Fe, Nb, Ce, Mn.

The total content of the transition metals in the catalyst is between 0.5 to 6% by weight, preferably between 0.5 and 5% by weight, and even more preferably between 1 and 4% by weight, relative to the mass. total of the final catalyst, in its anhydrous form. This content takes into account the copper provided by the copper source introduced in step i) of the preparation process.

For catalysts which contain only copper as transition metal, the total mass content of the copper catalyst is between 0.5 and 6%, preferably between 0.5 and 5%, preferably between 1 and 4%, and more preferably still between 1.5 and 3.5%, based on the total weight of the anhydrous final catalyst. For materials comprising copper and another transition metal, such as, preferably, Fe, Nb, Ce, Mn, the copper content of the catalyst is between 0.05 and 2% by weight, preferably 0.5 and 2% by weight, whereas the content of the other transition metal is preferably between 1 and 4% by weight, the content of transition metals being given as a percentage by weight relative to the total weight of the anhydrous final catalyst. In both cases, the copper comes from the synthesis of the zeolite composite material, more practically from the copper source introduced in step i) of the process for preparing the catalyst according to the invention, and the exchange of the possible step iii).

The catalyst according to the invention may also comprise other elements, such as, for example, alkali and / or alkaline earth metals, for example sodium, originating especially from synthesis, in particular from the compounds of the reaction medium of step i ) of the process for preparing said catalyst.

Process for preparing the catalyst

Step i) mixing

The preparation process according to the invention comprises a step i) of mixing in an aqueous medium at least one zeolite of structural type FAU having a molar ratio

between 2 and 200, of at least one nitrogen-containing organic compound R, R being 1,5-bis (methylpiperidinium) pentane dihydroxide, 1,6-bis (methylpiperidinium) hexane dihydroxide and / or 1-dihydroxide. , 7-bis (methylpiperidinium) heptane, at least one source of at least one alkali metal and / or one alkaline earth metal M of valence n, n being an integer greater than or equal to 1, of at least an organic complexing agent and at least one copper source, the reaction mixture having the following molar composition:

(Si0 ₂ (FAU)) / (Al 203 (FAU)) between 2 and 200, preferably between 4 and 100;

between 1 and 100, preferably between 5 and 60;

R / (Si0 ₂ (FAU)) of between 0.01 and 0.6, preferably between 0.05 and 0.5;

M _{2 / n} 0 / (Sl0 ₂ (FAU)) of between 0.005 and 0.7, preferably between 0.01 and 0.5;

CuO / (Si0 _{2 (FAU)} ) of between 0.005 and 0.06, preferably between 0.006 and 0.05;

OCPLX / CuO between 0.8 and 2, preferably between 0.8 and 1.5, and preferably between 0.9 and 1.2; wherein Si0 ₂ <FAU> is the molar amount of SiO ₂ provided by the FAU zeolite, Al ₂ O ₃ ₍ FAU) the molar amount of Al ₂ O ₃ provided by the FAU zeolite, H ₂ 0 the molar amount of water in the reaction mixture, R is the molar amount of said nitrogenous organic compound, M _{2 / n} 0 the molar amount of M _{2 / n} O provided by the FAU zeolite and by the source of the alkali metal and / or alkaline earth metal, OCPLX the molar amount of organic complexing agent and CuO the molar amount of CuO supplied by the copper source.

According to the invention, at least one, preferably one, zeolite of structural type FAU having a SiO ₂ / Al ₂ O ₃ ratio of between 2 and 200, preferably between 4 and 100, is incorporated in the reaction mixture as a source. silicon and aluminum.

The zeolite of structural type FAU starting can be obtained by any method known to those skilled in the art, such as for example by direct synthesis in the case of a zeolite FAU having a molar ratio Si0 ₂ / Al ₂ 0 ₃ less than 6 or by steaming and / or acid washing of a zeolite of structural type FAU having an SiO ₂ / Al ₂ O ₃ molar ratio of less than 6 in the case of a FAU zeolite having a ratio molar Si0 ₂ / Al ₂ 0 ₃ greater than or equal to 6. Said zeolite of structural type FAU starting can be used in its sodium form or any other form. It may, for example, before being used in the process according to the invention, undergo an exchange of part or all of its sodium cations with ammonium cations, followed or not by a calcination step. Among the sources of FAU with an Si0 ₂ / Al ₂ O ₃ molar ratio of between 2 and 200, preferably between 4 and 100, can be mentioned the Y-type commercial zeolites produced by Zeolyst and by TOSOH, for example CBV100 commercial zeolites. , CBV600, CBV712, CBV720, CBV760 and CBV780, and commercial zeolites HSZ-320HOA, HSZ-350HUA, HSZ-360HUA and HSZ-385HUA.

According to the invention, the reaction mixture comprises at least one, preferably a nitrogenous organic compound R, chosen from 1,5-bis (methylpiperidinium) pentane dihydroxide and 1,6-bis (methylpiperidinium) hexane dihydroxide. , 1,7-bis (methylpiperidinium) heptane dihydroxide and mixtures thereof, said compound being incorporated into the reaction mixture as a structurant. Preferably, the structurant R incorporated in the reaction mixture is 1,6-bis (methylpiperidinium) hexane dihydroxide. The anion associated with the quaternary ammonium cations present in the structuring nitrogenous organic species is the hydroxide anion. According to the invention, at least one, preferably one, source of at least one alkali metal and / or one alkaline earth metal M of valence n, n being an integer greater than or equal to 1, is used in the reaction mixture of step i). Advantageously, the alkali metal and / or alkaline earth metal M is chosen from lithium, potassium, sodium, magnesium, calcium and the mixture of at least two of these metals. Most preferably, M is sodium. Preferably, the source of at least one alkali metal and / or alkaline earth metal M is sodium hydroxide.

According to the invention, at least one, preferably one, source of copper is incorporated in the reaction mixture of step i). According to the invention, a copper source is a species capable of releasing copper in solution, advantageously in reactive form, for example sulphates, nitrates, chlorides, oxalates, organometallic complexes of copper or their mixtures. Preferably, the copper source is selected from copper sulphates and copper nitrates.

According to the invention, at least one, preferably an organic complexing agent (OCPLX) is incorporated in the reaction medium during step i) of the process according to the invention. This organic complexing agent will be able to react with copper in solution, released by the copper source, to create in situ an organic complex of copper. The organic complexing agent (OCPLX) according to the invention is advantageously triethylenetetramine (TETA) or tetraethylenepentamine (TEPA).

Step i) makes it possible to obtain a homogeneous precursor gel.

In a particular embodiment of the invention, the reaction mixture of step i) also comprises at least one additional source of an oxide X0 ₂ , X being a tetravalent element chosen from the group formed by silicon and germanium. titanium, preferably silicon, so that, in the reaction mixture, the molar ratio X0 ₂ / SiO _{2 (} F _AU) is between 0.001 and 1, preferably between 0.001 and 0.9 and more preferably between 0.001 and 0.001. and 0.01, and that the molar ratio (X0 ₂ + Si0 _{2 (FAU)} ) / (AI ₂ 0 _{3 (FAU)} ) is advantageously between 2 and 200, preferably between 4 and 100, X0 ₂ being the amount molar amount of X0 ₂ provided by the additional source of said oxide X0 ₂ , SI0 _{2 (FAU)} the molar amount of Si0 ₂ provided by the zeolite FAU and AI ₂ 0 _{3 (} F _AU) the molar amount of Al ₂ 0 ₃ provided by the zeolite FAU. Advantageously, in this embodiment, the molar composition of the reaction mixture is:

(X0 ₂ + Si0 _{2 (} F _AU >) / AI ₂ 0 ₃ between 2 and 200, preferably between 4 and 100; H ₂ O / (XO ₂ + SiO _{2 (FAU)} ) of from 1 to 100, preferably from 5 to 60;

R / (X0 ₂ + SiO _{2 (FAU)} ) of between 0.01 and 0.6, preferably between 0.05 and 0.5;

M 2 / n 0 / (XO ₂ + SiO _{2 (FAU)} ) of between 0.005 and 0.7, preferably between 0.01 and 0.5;

Cu0 / (X0 ₂ + SiO _{2 (FAU)} ) of between 0.005 and 0.06, preferably between 0.006 and 0.05;

OCPLX / CuO between 0.8 and 2, preferably between 0.8 and 1.5, and preferably between 0.9 and 1, 2. in which X0 ₂ is the molar amount of X0 ₂ provided by the additional source of said oxide X0 ₂ , Si0 _{2 (F} AU) is the molar amount of Si0 ₂ provided by the zeolite FAU, Al ₂ 0 ₃ ₍ FAU) molar amount of Al ₂ 0 ₃ provided by the zeolite FAU, H ₂ 0 the molar amount of water present in the reaction mixture, R the molar amount of said nitrogenous organic compound, M _{2 / n} O the molar amount of M _{2 / n} O provided by the zeolite FAU and the source of alkali metal and / or alkaline earth metal, OCPLX the molar amount of organic complexing agent and CuO the molar amount of CuO provided by the copper source.

In another particular embodiment of the invention, the reaction mixture of step i) also comprises at least one additional source of an oxide Y ₂ O ₃ , Y being a trivalent element chosen from the group formed by the aluminum, boron and gallium, preferably aluminum, so that in the reaction mixture, the molar ratio Y ₂ O ₃ / Al ₂ O _{3 (FAU)} is between 0.001 and 10, preferably between 0.001 and 5, preferably between 0.001 and 4, and that the molar ratio Si0 _{2 (FAU)} / (Al ₂ O _{3 (F} AU> + Y ₂ 0 ₃ ) is advantageously between 2 and 200, preferably between 4 and 100, SiO _{2 (F} AU) being the molar amount of SiO ₂ provided by the zeolite FAU, Al ₂ 0 _{3 (F} AU) the molar amount of Al ₂ O ₃ provided by the zeolite FAU and Y ₂ 0 ₃ the molar amount of Y ₂ 0 ₃ provided by the additional source of said oxide Y ₂ 0 _3. Advantageously, in this embodiment, the molar composition of the mixture reacts. l is:

+ Y ₂ O ₃ ) from 2 to 200, preferably from 4 to 100;

H ₂ O / (SiO _{2 (FAU)} ) of from 1 to 100, preferably from 5 to 60;

R / (SiO _{2 (} F _AU) ) between 0.01 and 0.6, preferably between 0.05 and 0.5; M ₂ / n 0 / (SiO ₂ (FAU)) of between 0.005 and 0.7, preferably between 0.01 and 0.5;

Cu0 / (Si0 _{2 (FAU)} ) of between 0.005 and 0.06, preferably between 0.006 and 0.05;

OCPLX / CuO between 0.8 and 2, preferably between 0.8 and 1.5, and preferably between 0.9 and 1.2; in which Si0 _{2 (F} AU) is the molar amount of SiO ₂ provided by the zeolite FAU, Y ₂ 0 ₃ is the molar amount of Y ₂ 0 ₃ provided by the additional source of said oxide Y ₂ 0 ₃ , Al ₂ 0 ₃ _(FAU) the molar amount of Al ₂ O ₃ provided by the zeolite FAU, H ₂ 0 the molar amount of water present in the reaction mixture, R the molar amount of said nitrogenous organic compound, M _{2 / n} O the molar amount of M _{2 / n} O provided by the zeolite FAU and the source of alkali metal and / or alkaline earth metal, OCPLX the molar amount of organic complexing agent and CuO the molar amount of CuO provided by the copper source.

In a third particular embodiment, the reaction mixture of step i) also comprises at least one additional source of an oxide X0 ₂ , X being a tetravalent element chosen from the group formed by silicon, germanium and titanium. , preferably silicon, and at least one additional source of an oxide Y ₂ O ₃ , Y being a trivalent element selected from the group consisting of aluminum, boron and gallium, preferably aluminum, of in that the reaction mixture of stage i) advantageously contains between 20 and 95% by weight, preferably between 50 and 95% by weight, preferably between 60 and 90% by weight and even more preferably between 65 and 85% by weight, zeolite of structural type FAU with respect to the total mass of the trivalent and tetravalent elements of the mixture, in their oxide form; the molar ratio X0 ₂ / SiO _{2 (FAU)} in the reaction mixture is between 0.001 and 1, preferably between 0.001 and 0.9 and more preferably between 0.001 and 0.01; the molar ratio Y ₂ O ₃ / Al ₂ O _{3 (F} AU) in the reaction mixture is between 0.001 and 10, preferably between 0.001 and 5, preferably between 0.001 and 4; and the molar ratio (X0 ₂ + SiO _{2 (} F _AU ) / (Al ₂ O _{3 (F} AU) + Y ₂ O ₃ ) in the reaction mixture is between 2 and 200, preferably between 4 and 100, X0 ₂ being the molar amount of X0 ₂ provided by the additional source of said oxide X0 ₂ , Si0 _{2 (FAU)} being the molar amount of Si0 ₂ provided by said zeolite FAU, AI ₂ 0 _{3 (FAU)} being the molar amount of Al ₂ 0 ₃ provided by said zeolite FAU and Y ₂ 0 ₃ being the molar amount of Y ₂ 0 ₃ provided by the additional source of said oxide Y ₂ 0 ₃ .

Advantageously, in this embodiment, the molar composition of the reaction mixture is:

(X0 ₂ + SiO _{2 (FAU)} ) / (Al ₂ O _{3 (FAU)} + Y ₂ O ₃ ) from 2 to 200, preferably from 4 to 100;

H ₂ O / (XO ₂ + SiO _{2 (FAU)} ) of from 1 to 100, preferably from 5 to 60;

M _{2 / n} 0 / (X0 ₂ + SiO _{2 (FAU)} ) of between 0.005 and 0.7, preferably between 0.01 and 0.5;

Cu0 / (X0 ₂ + SI0 _{2 (} F _AU) ) between 0.005 and 0.06, preferably between 0.006 and 0.05;

OCPLX / CuO between 0.8 and 2, preferably between 0.8 and 1.5, preferably between 0.9 and 1.2; in which X0 ₂ is the molar amount of X0 ₂ provided by the additional source of said oxide X0 ₂ , Si0 _{2 (FA} u ₎ is the molar amount of SiO ₂ provided by the zeolite FAU, Y ₂ 0 ₃ is the molar amount of Y ₂ 0 ₃ provided by the additional source of said oxide Y ₂ O ₃ , Al ₂ O ₃ _(FAU) the molar amount of Al ₂ O ₃ provided by the zeolite FAU, H ₂ 0 the molar amount of water present in the reaction mixture , R the molar amount of said nitrogenous organic compound, M _{2 / n} 0 the molar amount of M _{2 / n} O provided by the FAU zeolite and the source of the alkali metal and / or alkaline earth metal, OCPLX the molar amount of organic complexing agent and CuO the molar amount of CuO provided by the copper source.

The optional addition of at least one additional source of an oxide X0 ₂ and / or at least one additional source of an oxide Y ₂ O _{3 in} particular makes it possible to adjust the molar ratio of all the tetravalent elements. , expressed in their oxide form, with respect to the set of trivalent elements, expressed in their oxide form, that is to say the ratio molar (X0 ₂ + Si0 _{2 (FAU)} ) / (AI ₂ 0 _{3 (FAU)} + Y ₂ O ₃ ), precursor gel obtained at the end of step i) of the process according to the invention.

The additional source (s) of oxide X0 ₂ may be any compound comprising the tetravalent element X, X being chosen from the group formed by silicon, germanium and titanium, preferably silicon, and can release this element in aqueous solution in reactive form.

When X is titanium, Ti (EtO) ₄ is advantageously used as a source of titanium.

In the preferred case where X is silicon, the silicon source may be any of the sources commonly used for the synthesis of zeolites, for example powdered silica, silicic acid, colloidal silica, dissolved silica or tetraethoxysilane (TEOS). Among the silicas in powder form, it is possible to use precipitated silicas, especially those obtained by precipitation from an alkali metal silicate solution, pyrogenic silicas, for example "CAB-O-SIL" or "Aerosil" and silica gels. Colloidal silicas having different particle sizes, for example having a mean equivalent diameter of between 10 and 15 nm or between 40 and 50 nm, such as those sold under registered trademarks such as "LUDOX", may be used. Preferably, the silicon source is Aerosil.

The additional source (s) of oxide Y ₂ O ₃ may be any compound comprising the trivalent element Y, Y being chosen from the group formed by aluminum, boron and gallium. , preferably aluminum, and can release this element in aqueous solution in reactive form. Element Y may be incorporated into the mixture in an oxidized form YO _b with 1 <b <3 (b being an integer or a rational number) or in any other form.

In the preferred case where Y is aluminum, the aluminum source is preferably amorphous aluminum hydroxide or an aluminum salt, for example chloride, nitrate, or sulphate, sodium aluminate , an aluminum alkoxide, or alumina proper, preferably in hydrated or hydratable form, such as for example colloidal alumina, pseudoboehmite, gamma alumina or alpha or beta trihydrate. Mixtures of the sources mentioned above can also be used.

Step i) of mixing the process according to the invention is carried out until a homogeneous reaction mixture, called gel or precursor gel, is obtained. Preferably, step i) of mixing is carried out for a duration greater than or equal to 10 minutes and advantageously for less than 2 hours, in particular less than 1.5 hours, preferably at room temperature and preferably with stirring, at low or high shear rate, the stirring system being any system known to those skilled in the art, for example a mechanical stirrer to pale or a turbine. During this step i) of mixing, the aqueous solvent introduced can possibly partially evaporate.

It may be advantageous to add crystalline seeds of an AFX structural type zeolite, a BEA structural type zeolite and / or a copper-containing AFX-BEA composite material, to the reaction mixture during said step i) of the process of the invention, in order to reduce the time required for the formation of the crystals of the targeted material and / or the total crystallization time. Said crystal seeds also promote the formation of said copper-containing zeolite composite material AFX-BEA at the expense of impurities other than said zeolite composite material. The crystalline seeds are generally added in a proportion of between 0.01 and 10% by weight relative to the total weight of the sources of said tetravalent (s) and trivalent (s) element (s) in anhydrous form used in the reaction mixture, said seeds crystallins are not taken into account in the total weight of the sources of the tetravalent and trivalent elements. Said seeds are also not taken into account to determine the molar composition of the reaction mixture and / or gel, defined further, that is to say in the determination of different molar ratios of the composition of the reaction mixture.

Advantageously, step i) of the process according to the invention comprises a step of maturing the reaction mixture, carried out before the hydrothermal crystallization. This ripening step makes it possible to control the size of the crystals of the composite material. Said ripening also promotes the formation of said zeolite composite material to the detriment of impurities. The ripening of the reaction mixture during said step i) of the process of the invention can be carried out at ambient temperature or at a temperature of between 20 and 100 ° C., with or without stirring, for a period advantageously between 30 minutes and 48 hours.

Step ii) hydrothermal treatment

The preparation process according to the invention comprises a step ii) hydrothermal treatment of said precursor gel obtained at the end of step i), optionally matured, at a temperature between 120 ° C and 220 ° C, preferably between 150 ° C and 195 ° C, during a duration of between 12 hours and 15 days, preferably between 12 hours and 12 days, and more preferably between 12 hours and 8 days. Advantageously, the hydrothermal treatment is carried out at the autogenous reaction pressure.

The hydrothermal treatment is generally carried out with stirring or without stirring, preferably with stirring. Any stirring system known to those skilled in the art can be used, for example inclined blades with counter-blades, stirring turbines, Archimedean screws.

These operating conditions make it possible to obtain the crystallization, preferably complete, of the composite material in question. Crystallization is considered complete as soon as no more presence of amorphous product or zeolite FAU is detected by XRD analysis of a sample of the reaction medium extracted during the synthesis. According to the invention, this hydrothermal treatment step ii) can also be called a crystallization step, a reaction step or a synthesis step. The crystallized solid phase obtained is called "solid".

At the end of the reaction, the solid phase formed is advantageously filtered, washed, preferably with water, preferably deionized, and then preferably dried. The drying is generally carried out at a temperature between 20 and 150 ° C, preferably between 60 and 100 ° C for a period of between 5 and 24 hours.

The loss on ignition (PAF) of said solid obtained after drying (when the latter is carried out at the end of step ii)) is generally between 5 and 15% by weight. According to the invention, the loss on ignition of a sample, designated by the acronym PAF, corresponds to the mass difference of the sample tested before and after a heat treatment at 1000 ° C. for 2 hours. It is expressed in% corresponding to the percentage of loss of mass. The loss on ignition generally corresponds to the loss of solvent (such as water) contained in the solid but also to the elimination of organic compounds contained in the mineral solid constituents.

Step iii) possible exchange

Advantageously, the process for preparing the catalyst according to the invention optionally comprises at least one ion exchange step comprising contacting the solid obtained at the end of the preceding step, that is to say the aluminosilicate material. composite obtained at the end of step ii) or the calcined and calcined composite aluminosilicate material obtained from step iv) in the case where the steps iii) and iv) are inverted, with at least one solution comprising at least one species capable of releasing a transition metal, preferably copper, in solution in reactive form, preferably with stirring, at room temperature for a period of between 1 hour and 2 days, advantageously between 0, 5 days and 1.5 days, the concentration of said species capable of releasing the transition metal in said solution is a function of the amount of additional transition metal that is to be incorporated in said solid. Preferably, the ion exchange step iii), when it is present in the process for preparing the catalyst according to the invention, is carried out at the end of the hydrothermal treatment step ii).

The transition metal released in the exchange solution is selected from the group consisting of: Ti, V, Mn, Mo, Fe, Co, Cu, Cr, Zn, Nb, Ce, Zr, Rh, Pd, Pt , Au, W, Ag. Preferably, the transition metal is Fe, Cu, Nb, Ce or Mn, preferably Fe or Cu and preferably Cu.

According to the invention, the term "species capable of releasing a transition metal" means a species capable of dissociating in an aqueous medium, such as, for example, sulphates, nitrates, chlorides, oxalates or organometallic complexes of a transition metal or mixtures thereof. Preferably, the species capable of releasing a transition metal is a sulphate or a nitrate of said transition metal.

Advantageously, the process for preparing the catalyst according to the invention comprises a step iii) ion exchange by contacting the solid with a solution comprising at least one species, preferably a single species, capable of releasing a transition metal, preferably iron or copper, preferably copper, or by bringing the solid into contact successively with different solutions each comprising at least one, preferably only one, species capable of releasing a transition metal, the various solutions advantageously comprising species able to release a different transition metal.

At the end of the exchange, the solid obtained is advantageously filtered, washed, for example with deionized water, and preferably then dried to obtain a powder. In the case where step iii) comprises successive contacts of the solid with different solutions, the solid obtained after each contacting can be advantageously filtered, washed, for example with deionized water, and then preferably dried. . The drying is generally carried out at a temperature between 20 and 150 ° C, preferably between 60 and 100 ° C for a period of between 5 and 24 hours. According to the invention, the solution with which the solid is brought into contact comprises at least one species capable of releasing a transition metal, preferably a single species capable of releasing a transition metal, preferably iron or copper, preferentially the copper.

The total amount of transition metal, preferably iron or copper, preferably copper, contained in said final catalyst is between 0.5 and 6% by weight, preferably between 0.5 and 5% by weight, and even more preferably between 1 and 4% by weight, based on the total weight of the catalyst in its anhydrous form, the amount of copper introduced with the copper source incorporated in the reaction mixture of step i) of the process of the invention being understood.

The incorporation of a transition metal, in particular copper, in two stages, by direct incorporation during step i) of mixing and ion exchange during step iii) of the process according to the invention, allows surprisingly, to obtain catalysts having better properties, particularly in selective NO _x reduction applications, than solids comprising the same copper content, said copper having been incorporated in a single step by direct incorporation or by exchange.

According to one embodiment of the invention, the catalyst contains only copper as a transition metal and is prepared by a process comprising an ion exchange step iii), the solid to be treated (that is to say the composite aluminosilicate material obtained at the end of step ii) or dried and calcined composite aluminosilicate material obtained at the end of step iv when steps iii) and iv) are interchanged) being brought into contact with a solution comprising a species capable of releasing copper in solution in reactive form. Advantageously, the quantity of copper introduced during step i) represents between 0.05 and 1.5% by weight, the quantity of copper introduced during step iii) representing between 0.45 and 5% by weight, the amount of total copper contained in said final catalyst, that is to say at the end of the preparation process according to the invention, being between 0.5 and 6%, preferably between 0.5 and 5% mass and even more preferably between 1 and 4% by weight, all percentages being percentages by weight relative to the total mass of the final catalyst according to the invention in its anhydrous form, obtained at the end of the preparation process. Advantageously, between 25 and 45% by weight, preferably between 30 and 40% by weight, of the total copper of the catalyst according to the invention is introduced during stage i). Step iv) heat treatment

The preparation process according to the invention comprises a step iv) of heat treatment carried out at the end of the preceding step, that is to say at the end of the hydrothermal treatment step ii) or at the end of resulting from the optional step iii) of exchange, preferably at the end of step iii) ion exchange when the latter is carried out. When the process for preparing the catalyst according to the invention comprises step iii), the latter can advantageously be interchanged with step iv). Each of the two steps iii) and iv) can also possibly be repeated.

Said heat treating step iv) comprises drying the solid at a temperature of between 20 and 150 ° C., preferably between 60 and 100 ° C., for a duration of between 2 and 24 hours, followed by calcination in air, optionally dry, at a temperature between 450 and 700 ° C, preferably between 500 and 600 ° C for a period of between 2 and 20 hours, preferably between 5 and 10 hours, preferably between 6 and 9 hours, the flow rate of optionally dry air being preferably between 0.5 and 1.5 l / h / g of solid to be treated, preferably between 0.7 and 1.2 l / h / g of solid to be treated. The calcination may be preceded by a gradual rise in temperature.

The catalyst obtained at the end of step iv) of heat treatment is devoid of any organic species, in particular devoid of the organic template R and the organic complexing agent OCPLX.

The applicant has discovered that the catalyst obtained by the process according to the invention has different characteristics of a mechanical mixture of aluminosilicate materials of types AFX and BEA, comprising copper, generally introduced by ion exchange with one, the other or the mixture of the two zeolites AFX and BEA, known until now. In particular, the material obtained by the process according to the invention has improved properties for the conversion of NO _x . The present invention therefore also relates to a microporous aluminosilicate material of AFX / BEA structural type comprising copper, obtained or obtainable by a preparation process as described in the present application. Characterization of the catalyst prepared according to the invention

The catalyst according to the invention comprises a zeolite structure composed of a mixture of AFX and BEA structures according to the classification of the International Zeolite Association (IZA). This structure is characterized by X-ray diffraction (XRD).

The X-ray diffraction technique also makes it possible to determine the mass proportion of the mixture of zeolites AFX and BEA in said catalyst and the relative proportions of each zeolite, AFX and BEA. Advantageously, the overall mass proportion of zeolites AFX and BEA in the catalyst obtained is greater than or equal to 90%, preferably greater than or equal to 95%, preferably greater than or equal to 99% and even more preferably greater than or equal to 99%. , 8%, relative to the total mass of said catalyst, in its anhydrous form. In other words, the catalyst obtained comprises less than 10% by weight, preferably less than 5% by weight, preferably less than 1% by mass and even more preferably less than 0.2% by weight of impurities and / or crystalline or amorphous phase other than AFX and BEA (the terminals are not included). Very advantageously, the process of the invention leads to the formation of a catalyst comprising a zeolite structure composed of a mixture of zeolites AFX and BEA, free from any other crystalline or amorphous phase and / or any impurity.

The X-ray diffraction pattern (XRD) is obtained by radiocrystallographic analysis using a diffractometer using the conventional powders method with the copper Ko (1 = 1.540 °) radiation. From the position of the diffraction peaks represented by the angle θ2, the Bragg relation is used to _{calculate the} characteristic reticular equidistance of the sample. The measurement error A (d _h w) on d _h w is calculated by means of the Bragg relation as a function of the absolute error D (2Q) assigned to the measurement of 2Q. An absolute error D (2Q) equal to ± 0.02 ° is commonly accepted. The relative intensity l _rei assigned to each value of d _h w is measured from the height of the corresponding diffraction peak. Comparison of the diffractogram with the International Center for Diffraction Data (ICDD) databases using software such as DIFFRACT.SUITE allows the identification of the crystalline phases present in the material obtained.

The X-ray diffraction pattern of the AFX-BEA composite material containing copper obtained at the end of stage ii) of the process according to the invention or of the catalyst according to the invention, advantageously obtained at the end of the step iv) of the process of the invention, contains at least the lines at the values of d _h w given in Table 1. In the d _hki column, the average values of inter-reticular distances in Angstroms (A) are indicated. Each of these values shall be assigned the measurement error A (d _hki ) between ± 0,6A and ± 0,01A. Table 1: Mean values of d _h w and relative intensities measured on an X-ray diffraction pattern of X-BEA AFX composite material containing copper obtained at the end of step ii) of the process according to the invention or the catalyst according to the invention

where FF = very strong; F = strong; m = average; mf = weak medium; f = weak; ff = very weak. The relative intensity l _rei is given in relation to a scale of relative intensity where it is attributed a value of 100 to the most intense line of the X-ray diffraction pattern: ff <15;<F<30;<Mf<50; 50 <m <65; 65 <F <85;FF>85; 1 <ff-f <30;<Half or <65;<F-mf<50; 65 <F-FF <100;<Fm<65; 15? F-FF? 100.

According to the invention, the mass composition of the catalyst, in particular the relative mass fractions of zeolites of structural type AFX and structural type BEA present in said catalyst, is advantageously determined using a method similar to ASTM D3906. 03, by comparison of the peak areas at angles (20) 20.38 ± 0.1 (hkl: 21 1); 23.67 ± 0.1 (hl: 105); 26.1 ± 0.1 (hkl: 303) and 28.02 ± 0.1 (hkl: 106) x-ray diagrams obtained for the composite material according to the invention and a zeolite of structural type AFX reference, preferably high purity, preferably having a purity greater than or equal to 99.8%. The mass ratio of the two zeolites AFX and BEA in the composite material according to the invention is thus evaluated by comparing the sum of the areas of the peaks at the angles (20) mentioned above obtained for the composite material prepared according to the invention with that obtained for a reference sample of zeolite AFX and using the following calculation formula:

AFX / BEA = S _AFXc / (S _AFXr - S _AFXc ) where S _AFXC is the sum of the areas of the peaks present at the angles (2Q) 20.38 ± 0.1 (hkl: 211); 23.67 ± 0.1 (hl: 105); 26.1 ± 0.1 (hkl: 303) and 28.02 ± 0.1 (hkl: 106) of the diffractogram of the AFX-BEA composite material containing copper prepared according to the invention and S _AFXr is the sum of the areas of the peaks present at the angles (2Q): 20.38 (hk: 21 1); 23.67 (hl: 105); 26.1 (hkl: 303) and 28.02 (hkl: 106) of the diffractogram of pure AFX structural zeolite, used as a reference.

The qualitative and quantitative analysis of the chemical species present in the materials obtained is made by X-ray fluorescence spectrometry (FX). This is a technique of chemical analysis using a physical property of matter, the fluorescence of X-rays. The spectrum of X-rays emitted by the material is characteristic of the composition of the sample, by analyzing this spectrum, one can deduce the elemental composition, that is to say the mass concentrations in elements.

The loss on ignition (PAF) of the catalyst obtained after the drying step (and before calcination) or after the calcining step of step iv) of the process according to the invention is generally between 2 and 15% by weight, preferably between 5 and 15% by weight. The loss on fire the catalyst sample, designated by the acronym PAF, corresponds to the mass difference of the sample before and after heat treatment at 1000 ° C. for 2 hours. It is expressed in% corresponding to the percentage of loss of mass. The loss on ignition generally corresponds to the loss of solvent (such as water) contained in the solid but also to the elimination of organic compounds contained in the mineral solid constituents.

Use of the catalyst according to the invention

The invention also relates to the use of the catalyst according to the invention, advantageously directly prepared by or capable of being prepared by the process described above, for the selective reduction of NO _x by a reducing agent such as NH ₃ or H ₂ , advantageously shaped by deposition in the form of coating ("washcoat" according to English terminology) on a monolith (or structure), preferably a honeycomb structure mainly for mobile applications or a plate structure that is found especially for stationary applications.

The honeycomb structure is formed of parallel channels open at both ends (flow-through in English) or has porous filtering walls and in this case the adjacent parallel channels are alternately plugged on either side of the channels in order to force the flow of gas through the wall (wall-flow monolith in English). Said honeycomb structure thus coated constitutes a catalytic bread. Said structure may be composed of cordierite, silicon carbide (SiC), aluminum titanate (AITi), alpha alumina, mullite or any other material whose porosity is between 30 and 70%. Said structure may be made of sheet metal, stainless steel containing chromium and aluminum, FeCrAI type steel.

The quantity of catalyst according to the invention deposited on said honeycomb structure is between 50 to 180 g / l for the filtering structures and between 80 and 200 g / l for structures with open channels.

The catalyst according to the invention is advantageously associated with a binder such as ceria, zirconium oxide, alumina, non-zeolitic silica-alumina, titanium oxide, a mixed ceria-zirconia type oxide, a tungsten oxide and / or spinel, to be shaped by coating deposition. Said coating is advantageously applied to a monolithic structure, or monolith, very preferably to a honeycomb structure, by a method of deposit ("washcoating" in English) which consists of dipping the monolithic slurry catalyst powder according to the invention in a solvent, preferably water, and potentially binders, metal oxides, stabilizers or other promoters. This quenching step can be repeated until the desired amount of coating is reached. In some cases the slurry can also be sprayed within the monolith. The coating once deposited, the monolith is calcined at a temperature of 300 to 600 ° C for 1 to 10 hours.

Said monolithic structure may be coated with one or more coatings. The coating comprising the catalyst according to the invention is advantageously associated with, that is to say covers one or is covered by, another coating having pollutant adsorption capacities, in particular NOx, pollutants reduction in particular NOx or promoting the oxidation of pollutants, in particular that of ammonia.

Another possibility is to directly put the catalyst in the form of extruded. In this case, the structure obtained can contain up to 100% of catalyst according to the invention.

Said structure coated with the catalyst according to the invention or obtained by extrusion of the catalyst according to the invention is advantageously integrated in an exhaust line of an internal combustion engine, in particular operating mainly in a lean mixture, that is to say say in excess of air with respect to the stoichiometry of the combustion reaction as is the case for diesel engines for example. Under these operating conditions of the engine, the exhaust gases contain in particular the following pollutants: soot, unburned hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx). Upstream of said structure coated with the catalyst according to the invention can be placed an oxidation catalyst whose function is to oxidize the HC and the CO and a filter for removing soot from the exhaust gases, the function of said coated structure being to remove NOx, its operating range being between 100 and 900 ° C and preferably between 200 ° C and 500 ° C. Descriptions of figures

FIG. 1 represents the chemical formulas of the specific nitrogen-containing organic compounds which may be chosen as structuring agents in the process according to the invention.

FIG. 2 represents the X-ray diffraction pattern of the catalyst obtained after the heat treatment step iv) of Example 4.

FIG. 3 shows the conversion of NOx (expressed in%) as a function of the temperature (expressed in ° C), under Standard SCR conditions, obtained for the catalysts (Cu- AFX / BEA 1) (curve with circles), (Cu-AFX / BEA 2) (curve with squares) and (Cu- AFX / BEA 3) (curve with triangles), during the catalytic test according to Example 8. Figure 4 shows the conversion of NOx ( expressed in%) as a function of the temperature (expressed in ° C), under Standard SCR conditions, obtained for the catalyst (Cu- AFX / BEA 3) according to the invention (curve with the triangles) and the comparative catalyst (Cu - SSZ-16) (curve with the diamonds), during the catalytic test according to Example 9.

FIG. 5 shows the conversion of NOx (expressed in%) as a function of the temperature (expressed in ° C), under Standard SCR conditions, obtained for the catalyst (Cu- AFX / BEA 3) according to the invention (curve with the triangles) and the comparative material (Cu-SSZ-16 + Cu-BEA) prepared according to Example 7 by mechanical mixing (curve with the crosses), during the catalytic test according to Example 10.

The invention is illustrated by the following examples, which in no way present a limiting character.

EXAMPLES

Example 1 Preparation of 1,6-bis (methylpiperidinium) hexane dihydroxide

(structuring R).

50 g of 1,6-dibromohexane (0.20 mol, 99%, Alfa Aesar) are added to a 1 L flask containing 50 g of N-methylpiperidine (0.51 mol, 99%, Alfa Aesar) and 200 ml. ethanol. The reaction medium is stirred and refluxed for 5 hours. The mixture is then cooled to room temperature and filtered. The mixture is poured into 300 ml of cold diethyl ether and the precipitate formed is filtered off and washed with 100 ml of diethyl ether. The solid obtained is recrystallized from an ethanol / ether mixture. The solid obtained is dried under vacuum for 12 hours. 71 g of a white solid are obtained (ie a yield of 80%).

The product has the expected ¹ H NMR spectrum and corresponds to 1,6-bis (methylpiperidinium) hexane dibromide. ¹ H NMR (D ₂ O, ppm / TMS): 1.27 (4H, m); 1.48 (4H, m); 1.61 (4H, m); 1.70 (8H, m); 2.85 (6H, s); 3.16 (12H, m).

18.9 g of Ag ₂ 0 (0.08 mol, 99%, Aldrich) were added to a Teflon beaker of 250 ml containing 30 g of the dibromide of 1, 6-bis (methylpiperidinium) hexane (0.07 mol ) and 100 mL of deionized water. The reaction medium is stirred in the dark for 12 hours. The mixture is then filtered. The filtrate obtained is composed of an aqueous solution of 1,6-bis (methylpiperidinium) hexane dihydroxide. The assay of this species is carried out by proton NMR using formic acid as a standard. The value obtained is 21.56% by weight of 1,6-bis (methylpiperidinium) hexane dihydroxide.

Example 2 Preparation of a Catalyst According to the Invention

0.94 g of sodium hydroxide (98% by weight, Aldrich) are dissolved in 37.42 g of deionized water, with stirring (300 rpm) and at room temperature. 43.04 g of a 21.56% by weight aqueous solution of 1,6-bis (methylpiperidinium) hexane dihydroxide prepared according to Example 1 are added. The solution is then homogenized with stirring at 300 rpm for 10 minutes. 8.47 g of HY CBV780 zeolite (molar ratio SiO ₂ / Al ₂ O ₃ = 98.24, PAF = 8.52%, Zeolyst) are then added to the solution with stirring for 5 minutes. 0.88 g of amorphous gel of aluminum hydroxide (AI (OH) ₃ gel amorphous, 58.55% Al ₂ 0 _3, Merck) or an AI ₂ 0 ₃ molar ratio _{(9QI amorphous)} / AI ₂ 0 _{3 (FAU)} = 3.9, are introduced into the resulting solution, still with stirring. The mixture is then homogenized for 10 minutes at room temperature. In this solution, is added with stirring another solution obtained by dissolving 0.52 g of copper sulfate and 0.40 g of tetraethylenepentamine (TEPA) in 10.94 g of deionized water. The whole is stirred for a further 10 minutes at room temperature. The reaction mixture has the following molar composition: 100 SiO ₂ : 5 Al ₂ O ₃ : 9.3 Na ₂ O: 16.7 R: 1.65 CuO: 1.65 TEPA: 3673 H ₂ O, ie a molar ratio Si0 ₂ / Al ₂ O ₃ of 20.

The precursor gel obtained is introduced into a 160 mL stainless steel reactor, equipped with a stirring system comprising four inclined blades and counter-blades. The reactor is closed and heated at a temperature of 170 ° C for 48 hours with stirring at 200 rpm. The crystals obtained are separated by filtration and washed with deionized water until a pH of the washings of less than 8 is obtained. The washed material is then dried overnight at 100 ° C. The loss on ignition (PAF) of the dried solid, evaluated at 1000 ° C. for 2 hours, is 12.4%.

The dried solid is then introduced into a muffle furnace where a calcination step is carried out: the calcination cycle comprises a temperature rise of 1.5 ° C./min up to 200 ° C., a plateau maintained at 200 ° C. during 2 hours, a rise in temperature of 1 ° C / min up to 550 ° C followed by a plateau at 550 ° C maintained for 8 hours and then a return to ambient temperature.

The calcined solid product is analyzed by X-ray diffraction and identified as consisting of more than 99% by weight of a mixture of AFX zeolite (55% by mass relative to the material obtained in its anhydrous form) and BEA zeolite (45% by weight). mass relative to the material obtained in its anhydrous form) with a mass ratio of AFX / BEA = 1, 22. The material is also analyzed by X-ray fluorescence (FX): it contains 1.8% by mass of Cu.

The catalyst obtained is noted Cu-AFX / BEA 1.

Example 3 Preparation of a Catalyst According to the Invention

0.95 g of sodium hydroxide (98% by weight, Aldrich) are dissolved in 38.41 g of deionized water, with stirring (300 rpm) and at room temperature. 43.08 g of a 21.56 wt.% Aqueous solution of 1,6-bis (methylpiperidinium) hexane dihydroxide prepared according to Example 1 are added. The solution is then homogenized with stirring at 300 rpm for 10 minutes. 8.48 g of HY CBV780 zeolite (Si0 ₂ / Al ₂ O ₃ molar ratio = 98.24, PAF = 8.52%, of Zeolyst) are then added to the solution with stirring for 5 minutes. 0.88 g of amorphous gel of aluminum hydroxide (Al (OH) ₃ amorphous gel, 58.55% Al ₂ 0 _3, Merck), is one al20 molar ratio _{3 (amorphous gei)} / AI ₂ 0 _{3 (FAU)} = 3.9, are introduced into the resulting solution, still with stirring. The mixture is then homogenized for 10 minutes at room temperature. In this solution is added with stirring another solution obtained by dissolving 0.52 g of copper sulfate and 0.31 g of tetraethylenetetramine (TETA) in 10 g of deionized water. The whole is stirred for a further 10 minutes at room temperature. The reaction mixture has the following molar composition: 100 SiO ₂ : 5 Al ₂ O ₃ : 9.3 Na ₂ O: 16.7 R: 1.65 CuO: 1.65 TETA: 3673 H ₂ O, ie a molar ratio Si0 ₂ / Al ₂ O ₃ of 20.

The precursor gel obtained is introduced into a 160 mL stainless steel reactor, equipped with a stirring system comprising four inclined blades and counter-blades. The reactor is closed and heated at a temperature of 170 ° C for 36 hours with stirring at 200 rpm. The crystals obtained are separated by filtration and washed with deionized water until a pH of the washings of less than 8 is obtained. The washed material is then dried overnight at 100 ° C. The loss on ignition (PAF) of the dried solid, evaluated at 1000 ° C. for 2 hours, is 1.16%.

The calcined solid product is analyzed by X-ray diffraction and identified as consisting of more than 99% by weight of a mixture of AFX zeolite (69% by mass relative to the material obtained in its anhydrous form) and of BEA zeolite (31% by weight). mass relative to the material obtained in its anhydrous form) with a mass ratio of AFX / BEA = 2.2. Analysis of the X-ray fluorescence (FX) mixture indicates a value of 2.0% Cu.

The catalyst obtained is noted Cu-AFX / BEA 2.

Example 4 Preparation of a Catalyst According to the Invention

Mixing step

0.95 g of sodium hydroxide (98% by weight, Aldrich) are dissolved in 38.6 g of deionized water, with stirring (300 rpm) and at room temperature. 43.2 g of a solution 21%, 56% by weight of 1,6-bis (methylpiperidinium) hexane dihydroxide prepared according to Example 1 are added. The solution is then homogenized with stirring at 300 rpm for 10 minutes. 8.50 g of HY CBV780 zeolite (Si0 ₂ / Al ₂ O ₃ molar ratio = 98.24, PAF = 8.52%, Zeolyst) are added to the solution, which is then left stirring for 10 minutes. Then 0.88 g of amorphous gel of aluminum hydroxide (Al (OH) ₃ amorphous gel, 58.55% Al ₂ O ₃ , Merck), or a molar ratio Al ₂ O _{3 (gei amorPhe)} / _Al ₂ 0 _{3 (FAU)} = 3.9, are introduced into the solution thus obtained, still stirring. The mixture is then homogenized for 10 minutes at room temperature. In this solution is added with stirring another solution obtained by dissolving 0.26 g of copper sulfate and 0.20 g of tetraethylenepentamine (TEPA) in 10 g of deionized water. The whole is stirred for a further period of 10 minutes at room temperature. The reaction mixture has the following molar composition: 100 SiO ₂ : 5 Al ₂ O ₃ : 9.3 Na ₂ O: 16.7 R: 0.83 CuO: 0.83 TEPA: 3673 H ₂ 0, ie a molar ratio Si0 ₂ / Al ₂ O ₃ of 20.

Hydrothermal treatment stage

The precursor gel obtained is introduced into a 160 mL stainless steel reactor, equipped with a stirring system comprising four inclined blades and counter-blades. The reactor is closed and heated at a temperature of 170 ° C for 48 hours with stirring at 200 rpm. The crystals obtained are separated by filtration and washed with deionized water until a pH of the washings of less than 8 is obtained.

Heat treatment step (drying and calcination)

The washed material is then dried overnight at 100 ° C. The loss on ignition (PAF) of the dried solid, evaluated at 1000 ° C. for 2 hours, is 1.15%. The solid is then introduced into a muffle furnace where a calcination step is carried out: the calcination cycle comprises a rise in temperature of 1.5 ° C./min up to 200 ° C., a plateau at 200 ° C. maintained during 2 hours, a temperature rise of 1 ° C./min up to 550 ° C. followed by a plateau at 550 ° C. held for 8 hours and then a return to ambient temperature.

The calcined solid product is analyzed by X-ray diffraction. The X-ray diagram obtained is shown in FIG. 2. The calcined solid product is identified as consisting of more than 95% by weight of a mixture of zeolite AFX (60% relative to the material obtained in its anhydrous form) and BEA zeolite (40% by weight relative to to the material obtained in its anhydrous form) with a mass ratio of AFX / BEA = 1.5. The material is also analyzed by X-ray fluorescence (FX): it contains 1.0% by weight of Cu.

Ionic ion exchange

The composite material obtained, composed of a composite structure AFX-BEA and containing copper, and calcined is brought into contact with an aqueous solution of [Cu (NH ₃ ) 4] (NO ₃ ) 2 for 1 day with stirring at room temperature. room. The final solid is separated, washed and recovered.

Heat treatment step

The solid, recovered after contacting the [Cu (NH ₃ ) ₄ ] (NO ₃ ) _{2 solution} and washing, is dried at 100 ° C. for 4 hours, calcined under an air stream at 550 ° C. during 8 hours.

The calcined solid product is analyzed by X-ray diffraction and identified as consisting of a mixture of structural type zeolites AFX and BEA with a mass ratio of AFX / BEA = 1.5.

X-ray fluorescence (FX) chemical analysis gives a mass percentage of Cu of 2%.

The catalyst obtained is noted Cu-AFX / BEA 3.

Example 5 Preparation of a Comparative Catalyst Based on AFX

In this example, a zeolite SSZ-16 is synthesized and then exchanged with Cu according to the prior art. In this example, the copper is introduced by ion exchange.

Mixing step

17.32 g of sodium hydroxide are dissolved in 582.30 g of deionized water, with stirring (300 rpm) and at room temperature. 197.10 g of sodium silicate are added to this solution and the mixture is homogenized with stirring (300 rpm at room temperature, 9.95 g of NaY CBV100 zeolite are then added with stirring (300 rpm) and The solution is then continued until the zeolite is dissolved, 43.67 g of the DABCO-C4 structurant are dissolved in the solution obtained, and the mixture is then homogenized with stirring (450 rpm) for 30 minutes at room temperature. The reaction mixture has the following molar composition: 100 SiO ₂ : 1, 67 Al ₂ O ₃ : 50 Na ₂ O: 10 DABCO-C 4: 4000 H ₂ O

Step of ripening

The reaction mixture obtained in the mixing step is kept at room temperature with stirring for 24 hours.

Hydrothermal treatment stage

The gel obtained is left in an autoclave at a temperature of 150 ° C. for 6 days with stirring (200 rpm). The crystals obtained are separated and washed with deionized water until a pH of the washings of less than 8 is obtained. The washed material is dried. A DRX analysis shows that the product obtained is a zeolite SSZ-16 of synthetic and pure raw AFX structural type.

Heat treatment step

The crude synthetic zeolite SSZ-16 is treated under a flow of N ₂ dry at 550 ° C for 8 h, then calcined under a stream of dry air at 550 ° C for 8 h. The loss on ignition (PAF), evaluated at 1000 ° C for 2 hours, is 18% by weight.

NH ₄ ⁺ ion exchange on burned SSZ-16

The calcined zeolite SSZ-16 is brought into contact with a solution of 3 molar NH ₄ NO ₃ for 5 hours with stirring at room temperature. The ratio of the volume of NH ₄ NO ₃ solution to the mass of solid is 10. The solid obtained is filtered and washed and the exchange procedure is repeated again under the same conditions. The final solid is separated, washed and dried. A XRD analysis shows that the product obtained is a zeolite SSZ-16 in ammoniacal form (NH4-SSZ-16) of pure AFX structural type.

Heat treatment step

The zeolite SSZ-16 in ammoniacal form (NH4-SSZ-16) is treated under a stream of dry air at 550 ° C. for 8 hours with a temperature ramp of 1 ° C./min. The loss on ignition (PAF), evaluated at 1000 ° C for 2 hours, is 4% by weight. The product obtained is a zeolite SSZ-16 in protonated form (H-SSZ-16). Cu ion exchange on the H-SSZ-16

The zeolite H-SSZ-16 is brought into contact with a solution of [Cu (NH ₃ ) ₄ ] (NO ₃ ) ₂ for 1 day with stirring at room temperature. The final solid is separated, washed and dried.

The solid obtained after being placed in contact with the solution of [Cu (NH ₃ ) ₄ ] (NO ₃ ) ₂ is calcined under a stream of dry air at 550 ° C. for 8 hours.

A DRX analysis shows that the product obtained is a zeolite SSZ-16 of pure AFX structural type. X-ray fluorescence (FX) chemical analysis gives an Si0 ₂ / Al ₂ O ₃ molar ratio of 13 and a mass percentage of Cu of 2%.

The catalyst obtained is noted Cu-SSZ-16. Example 6 Preparation of a BEA Type Zeolite

In this example, a Beta zeolite exchanged with Cu is synthesized according to the prior art. In this example, the copper is introduced by ion exchange.

2 g of zeolite of structural type BEA in ammoniacal form (NH ₄ -BETA) with an SiO ₂ / Al ₂ O ₃ ratio = 25 (Zeolyst CP814E) are treated under a stream of dry air at 550 ° C. for 8 hours with a rise ramp of 1 ° C / min. The loss on ignition (PAF), evaluated at 1000 ° C for 2 hours, is 10.2% by weight. The product obtained is a BETA zeolite in protonated form (H-BETA). The zeolite H-BETA is brought into contact with a solution of [CU (NH ₃ ) ₄ ] (NO ₃ ) ₂ for 1 day with stirring at room temperature. The final solid is separated, washed and dried and calcined at 550 ° C. for 8 hours. A DRX analysis shows that the product obtained is a BEA type beta zeolite. X-ray fluorescence (FX) chemical analysis gives a mass percentage of Cu of 2%.

Example 7 Preparation of Comparative Material

In this example, the comparative material prepared is a mechanical mixture of a copper-exchanged AFX structural zeolite (Example 5) with a BEA-type zeolite exchanged with copper (Example 6).

120 mg of a zeolite of AFX structural type exchanged with copper as prepared in Example Example 5 and 80 mg of a zeolite of structural type BEA exchanged with copper prepared in Example Example 6 are mixed (ie an AFX / BEA mass ratio of (60% / 40%)).

The material obtained is noted (Cu-SSZ-16 + Cu-beta).

Example 8: Conversion of NOx into Standard SCR; comparison of the three catalysts Cu- AFXJBEA prepared according to the invention

A catalytic test for the reduction of oxides of nitrogen (NOx) by ammonia (NH ₃ ) in the presence of oxygen (O ₂ ) under Standard SCR conditions is carried out at different operating temperatures for the catalysts synthesized according to the example 2 (C-AFX / BEA 1), Example 3 (Cu-AFX / BEA 2) and Example 4 (Cu-AFX / BEA 3).

For the test of each sample, 200 mg of catalyst in powder form is placed in a quartz reactor. 218 L / h of a representative load of a mixture of exhaust gas of a diesel engine are fed into the reactor.

This feed has the following molar composition: 400 ppm NO, 400 ppm NH ₃ , 8.5% O ₂ , 9% CO ₂ , 10% H ₂ O, qpc N ₂ .

An FTIR analyzer makes it possible to measure the concentration of NO, NO ₂ , NH ₃ , N ₂ O, CO, CO ₂ , H ₂ O, O ₂ species at the outlet of the reactor. The NOx conversions are calculated as follows: Conversion = (NOx input -NOx output) / (NOx input).

The NOx conversion results obtained for the catalysts (Cu-AFX / BEA 1), (Cu- AFX / BEA 2) and (Cu-AFX / BEA 3) are shown in FIG.

It thus appears that the catalysts according to the invention make it possible to convert NOx.

Example 9 Conversion of NOx into Standard SCR and Fast-SCR: comparison of the Cu-AFX-BEA 3 sample synthesized according to the invention with the sample Cu-SSZ-16 synthesized according to the state of the art

A catalytic test for reduction of nitrogen oxides (NOx) by ammonia (NH ₃ ) in the presence of oxygen (O ₂ ) under Standard conditions SCR and Fast SCR is carried out at different operating temperatures for the catalyst (Cu -AFX / BEA 3) synthesized according to Example 4 and the sample Cu-SSZ-16 synthesized according to Example 5. 200 mg of material in powder form is placed in a quartz reactor. 218 L / h of a representative load of a mixture of exhaust gas of a diesel engine are fed into the reactor. This charge has the following molar composition:

for Standard SCR conditions: 400 ppm NO, 400 ppm NH ₃ , 8.5% 0 ₂ , 9% C0 ₂ , 10% H ₂ 0, qpc N ₂ ; and

for Fast SCR conditions: 200 ppm NO, 200 ppm N0 ₂ , 400 ppm NH ₃ , 8.5% 0 ₂ , 9% C0 ₂ , 10% H ₂ 0, qpc N ₂ .

An FTIR analyzer makes it possible to measure the concentration of NO, NO ₂ , NH ₃ , N ₂ O, CO, CO ₂ , H ₂ O, O ₂ species at the outlet of the reactor. The NOx conversions are calculated as follows: Conversion = (NOx input -NOx output) / NOx input.

Figure 4 shows the NOx conversion of the materials synthesized according to Example 4 (Cu-AFX / BEA 3) and Example 5 (Cu-SSZ-16) as a function of temperature under Standard SCR conditions.

The initiation temperatures obtained for the catalysts (Cu-AFX / BEA 3) and (Cu-SSZ-16) under Standard SCR conditions are given below:

The initiation temperatures obtained for the catalysts (Cu-AFX / BEA 3) and (Cu-SSZ-16) under Fast-SCR conditions are given below:

T50 is the temperature at which 50% of the NOx in the gas mixture is converted by the catalyst. T80 is the temperature at which 80% of the NOx in the gas mixture is converted by the catalyst. T90 is the temperature at which 90% of NOx of the gaseous mixture are converted by the catalyst. T100 is the temperature at which 100% NOx of the gas mixture is converted by the catalyst.

The Cu-AFX / BEA 3 catalyst, synthesized according to the invention, gives a very superior performance to the Cu-SSZ-16 material, synthesized according to the state of the art, in terms of priming temperatures and in NOx conversion. over the entire temperature range tested. Indeed, at the same conversion rate (50%, 80% or 90%), the initiation temperatures obtained with the catalyst according to the invention Cu-AFX / BEA 3 are lower compared to those obtained with the Cu material. -SSZ-16. A conversion of 100% is reached between 350 and 405 ° C for the Cu-AFX / BEA catalyst according to the invention whereas the comparative material Cu-SSZ-16, synthesized according to the state of the art, reaches only 90% conversion on the same temperature range.

The performances (NOx conversion and initiation temperatures) obtained under Fast SCR conditions with the catalyst according to the invention, Cu-AFX / BEA 3, are also higher than those obtained with the comparative material Cu-SSZ-16. The maximum conversion is 100% and is reached at 314 ° C while the material corresponding to a copper-exchanged AFX synthesized according to the state of the art (Cu-SSZ-16) reaches only 92% maximum for a temperature of 372 ° C.

In addition, nitrous oxide (N ₂ 0) emissions, in the case of the Cu-AFX / BEA 3 catalyst according to the invention, remain low over the entire temperature range tested (<15 ppm between 150 and 550 ° C. ).

Example 10: Conversion of NOx to Standard and Fast SCR; comparison of the sample Cu-AFX / BEA 3 synthesized according to the invention with a sample of the mechanical mixture (Cu- SSZ-16 + Cu-beta)

A catalytic test for the reduction of nitrogen oxides (NOx) by ammonia (NH ₃ ) in the presence of oxygen (O ₂ ) under Standard SCR and Fast SCR conditions is carried out at different operating temperatures for the carbon catalyst. AFX / BEA 3 synthesized according to Example 4 and the material (Cu-SSZ-16 + Cu-beta) prepared according to Example 7 and corresponding to a mechanical mixture of a zeolite of copper-exchanged AFX structural type (prepared according to Example 5) with a zeolite of structural type BEA exchanged with copper (prepared according to Example 6). 200 mg of material in powder form is placed in a quartz reactor. 218 l / h of a representative load of an exhaust gas mixture are fed into the reactor. This charge has the following molar composition:

- 400 ppm NO, 400 ppm NH ₃ , 8.5% 0 ₂ , 9% C0 ₂ , 10% H ₂ 0, qpc N ₂ for the conditions Standard SCR and

- 200 ppm NO, 200 ppm N0 ₂ , 400 ppm NH ₃ , 8.5% 0 ₂ , 9% C0 ₂ , 10% H ₂ 0, qpc N ₂ for Fast SCR conditions.

An FTIR analyzer makes it possible to measure the concentration of NO, NO ₂ , NH ₃ , N ₂ O, CO, CO ₂ , H ₂ O, O ₂ species at the outlet of the reactor. The NOx conversions are calculated as follows: Conversion = (NOx input -NOx output) / NOx input

Figure 5 shows the NOx conversion of the materials synthesized according to Example 4 (Cu-AFX / BEA 3) and Example 7 (Cu-SSZ-16 + Cu-beta) as a function of the temperature under Standard SCR conditions. .

The starting temperatures obtained for the catalysts under Standard-SCR conditions are given below:

The initiation temperatures obtained for the catalysts under Fast-SCR conditions are given below.

T50 is the temperature at which 50% of the NOx in the gas mixture is converted by the catalyst. T80 is the temperature at which 80% of the NOx in the mixture gaseous are converted by the catalyst. T90 is the temperature at which 90% of the NOx in the gas mixture is converted by the catalyst. T100 is the temperature at which 100% NOx of the gas mixture is converted by the catalyst.

The Cu-AFX / BEA 3 catalyst synthesized according to the invention gives a very superior performance to the material corresponding to a mechanical mixture of a copper-exchanged AFX synthesized according to the state of the art with a copper-exchanged commercial Beta zeolite. in terms of priming temperatures and NOx conversion over the entire temperature range tested under Standard SCR conditions. Indeed, at the same conversion rate (50%, 80% or 90%), the initiation temperatures obtained with the catalyst according to the invention Cu-AFX / BEA 3 are lower compared to those obtained with the Cu material. -SSZ-16 + Cu-beta obtained by mechanical mixing. A conversion of 100% is reached between 350 and 405 ° C for the Cu-AFX / BEA 3 material whereas the material corresponding to a mechanical mixture of a copper-exchanged AFX with a copper-exchanged Beta zeolite reaches only 85% of conversion.

The performances (NOx conversion and initiation temperatures) obtained under Fast SCR conditions with the catalyst according to the invention, Cu-AFX / BEA 3, are also higher than those obtained with the material (Cu-SSZ-16 + Cu -beta). The maximum conversion of 100% is reached at 314 ° C. with the catalyst according to the invention, Cu-AFX / BEA 3, whereas the material corresponding to a mechanical mixture of a copper-exchanged AFX with a Beta zeolite exchanged at copper reaches only 86% maximum for a temperature of 323 ° C.

In addition, the nitrous oxide (N ₂ 0) emissions, in the case of the Cu-AFX / BEA 3 catalyst according to the invention, are much lower (<15 ppm between 150 and 550 ° C.) than those obtained with the material (Cu-SSZ-16 + Cu-beta).

Claims

A process for the preparation of a catalyst comprising a zeolite composite material composed of a mixture of zeolites of structural type AFX and of structural type BEA and containing copper, comprising at least the following stages:

i) mixing in an aqueous medium, at least one zeolite of structural type FAU having a SiO _{2 (FAU)} / Al ₂ O ₃ <FAU> molar ratio of between 2 and 200, of at least one nitrogenous organic compound R selected from 1,5-bis (methylpiperidinium) pentane dihydroxide, 1,6-bis (methylpiperidinium) hexane dihydroxide, 1,7-bis (methylpiperidinium) heptane dihydroxide and mixtures thereof, from at least one source at least one alkali metal and / or alkaline earth metal M of valence n, n being an integer greater than or equal to 1, at least one organic complexing agent and at least one copper source, to obtain a precursor gel,

the reaction mixture having the following molar composition:

between 2 and 200;

H ₂ 0 / (Si0 ₂ (FAU>) of from 1 to 100;

R / (Si0 _{2 (FAU)} ) of from 0.01 to 0.6;

M _{2 / n} 0 / (Si0 ₂ (FAU)) of 0.005 to 0.7;

Cu0 / (Si0 _{2 (FAU)} ) of from 0.005 to 0.06;

OCPLX / CuO between 0.8 to 2;

wherein Si0 _{2 (FAU)} refers to the molar amount of SiO ₂ provided by the FAU zeolite, and Al ₂ 0 _{3 (FAU)} refers to the molar amount of Al ₂ O ₃ provided by the FAU zeolite, H ₂ 0 the molar amount of water present in the reaction mixture, R the molar amount of said nitrogenous organic compound, M _{2 / n} O being the molar amount of M _{2 / n} O provided by the zeolite FAU and the source of alkali metal and / or alkaline metal - earthy, OCPLX is the molar amount of organic complexing agent and CuO is the molar amount of CuO supplied by the copper source;

ii) the hydrothermal treatment of said precursor gel obtained at the end of step i) at a temperature of between 120 ° C. and 220 ° C., for a period of between 12 hours and 15 days, in order to obtain a crystallized solid phase, called "solid"; iii) optionally at least one ion exchange comprising contacting the solid obtained at the end of the preceding step with at least one solution comprising at least one species capable of releasing a transition metal in solution in reactive form with stirring at room temperature for a period of between 1 hour and 2 days;

iv) the heat treatment by drying of the solid obtained at the end of the preceding step at a temperature of between 20 and 150 ° C. for a duration of between 2 and 24 hours, followed by calcination under an air stream; at a temperature between 450 and 700 ° C for a period of between 2 and 20 hours.

2. Process according to claim 1, comprising the mixing step i), the hydrothermal treatment step ii), the ion exchange step iii) and the heat treatment step iv).

3. The method of claim 2, wherein steps iii) and iv) are inverted, and optionally repeated.

4. The method of claim 2 or 3, wherein step iii) is performed by contacting the solid with a solution comprising at least one, preferably a single species capable of releasing a transition metal or by setting successive contact of the solid with different solutions each comprising at least one, preferably a single species capable of releasing a transition metal, the various solutions advantageously comprising species capable of releasing a different transition metal.

5. Method according to one of claims 2 to 4, wherein the transition metal released in the solution of step iii) is selected from the group consisting of the following elements: Ti, V, Mn, Mo, Fe, Co , Cu, Cr, Zn, Nb, Ce, Zr, Rh, Pd, Pt, Au, W, Ag, the transition metal being preferably Fe, Cu, Nb, Ce or Mn, preferentially Fe or Cu and still most preferred Cu.

6. Method according to one of claims 2 to 5, wherein the transition metal content is between 0.5 to 6% by weight, preferably between 0.5 and 5% by weight, and even more preferably between 1 and 4% by weight, relative to the total mass of the final catalyst, in its anhydrous form, the amount of copper of the composite material of said catalyst being taken into account.

7. Method according to one of claims 1 to 6, wherein the catalyst contains only copper as a transition metal, at a content between 0.5 to 6% by weight, preferably between 0.5 and 5%. preferably between 1 and 4% and more preferably between 1, 5 and 3.5% based on the total weight of the anhydrous final catalyst.

8. Method according to one of claims 2 to 7, wherein the catalyst contains only copper as a transition metal, the amount of copper introduced in step i) representing between 0.05 and 1.5% by mass. , the quantity of copper introduced during step iii) representing between 0.45 and 5% by weight and the total amount of copper contained in said final catalyst is between 0.5 and 6%, preferably between 0.5 and 6%, 5% by mass and even more preferably between 1 and 4% by weight, all percentages being percentages by weight relative to the total mass of the final catalyst in its anhydrous form.

9. Method according to the preceding claim, wherein between 25 and 45% by weight, preferably between 30 and 40% by weight, of the total copper is introduced in step i).

10. Method according to one of claims 2 to 6, wherein the catalyst contains copper and another transition metal, such as preferably Fe, Nb, Ce, Mn, the copper content being between 0.05 and 2% mass, preferably 0.5 and 2% by mass, the content of the other transition metal being preferably between 1 and 4% by mass, the contents of transition metals being given as a percentage by weight relative to the total mass of the dry catalyst final.

1. Method according to one of the preceding claims, wherein the reaction mixture of step i) of the preparation process comprises at least one additional source of an oxide X0 ₂ , X being a tetravalent element chosen from the group formed. by silicon, germanium, titanium, preferably silicon, and at least one additional source of an oxide Y ₂ O ₃ , Y being a trivalent element selected from the group consisting of aluminum, boron and gallium preferably, aluminum, such that: the reaction mixture of step i) contains between 20 and 95% by weight, preferably between 50 and 95% by weight, preferably between 60 and 90% by weight and even more preferred between 65 and 85% by weight of zeolite of structural type FAU with respect to the total mass of the sources of the trivalent and tetravalent elements; the molar ratio X0 ₂ / SiO _{2 (FAU)} in the reaction mixture is between 0.001 and 1, preferably between 0.001 and 0.9 and more preferably between 0.001 and 0.01;

the molar ratio Y ₂ O ₃ / Al ₂ O _{3 (F} AU) in the reaction mixture is between 0.001 and 10, preferably between 0.001 and 5, preferably between 0.001 and 4; and

the molar ratio (X0 ₂ + SiO _{2 (F} AU)) / (Al ₂ O _{3 (FA} U) + Y ₂ O ₃ ) in the reaction mixture is between 2 and 200, preferably between 4 and 100,

X0 ₂ being the molar quantity of X0 ₂ provided by the additional source of said oxide X0 ₂ , Si0 _{2 (FA} u ₎ being the molar quantity of Si0 ₂ provided by said starting FAU zeolite, AI ₂ 0 _{3 (FA} u ₎ being the molar amount of Al ₂ O ₃ provided by said zeolite FAU and Y ₂ 0 ₃ being the molar amount of Y ₂ 0 ₃ supplied by the additional source of said oxide Y ₂ O ₃ ,

the molar composition of the reaction mixture being as follows:

(XO ₂ + SiO _{2 (FA} u ₎ ) / (Al ₂ O _{3 (FA} u ₎ + Y ₂ O ₃ ) from 2 to 200, preferably from 4 to 100;

H ₂ O / (XO ₂ + SiO _{2 (FA} u ₎ ) of from 1 to 100, preferably from 5 to 60;

^ _{2 / n} 0 / (X0 ₂ + Si0 _{2 (FAU)} ) between 0.005 and 0.7, preferably between 0.01 and 0.5;

Cu0 / (X0 ₂ + Si0 _{2 (FAU)} ) of between 0.005 and 0.06, preferably between 0.006 and 0.05;

OCPLX / CuO between 0.8 and 2, preferably between 0.8 and 1.5, preferably between 0.9 and 1, 2.

12. Method according to one of the preceding claims, wherein the nitrogenous organic compound R is 1,6-bis (methylpiperidinium) hexane dihydroxide.

13. Process according to one of the preceding claims, in which the hydrothermal treatment of stage ii) is carried out at a temperature of between 120 ° C and 220 ° C, preferably between 150 ° C and 195 ° C, during a duration of between 12 hours and 15 days, preferably between 12 hours and 12 days, and more preferably between 12 hours and 8 days, and preferably under autogenous pressure.

14. Method according to one of the preceding claims, wherein the step iv) heat treatment comprises drying the solid at a temperature between 20 and 150 ° C, preferably between 60 and 100 ° C, for a period of time between 2 and 24 hours, followed by a calcination under air, possibly dry, at a temperature between 450 and 700 ° C, preferably between 500 and 600 ° C for a period of between 5 and 10 hours, preferably between 6 and 9 hour, the air flow, optionally dry, preferably being between 0.5 and 1.5 L / h / g, preferably between 0.7 and 1.2 L / h / g of solid to be treated.

A catalyst comprising a composite material comprising a mixture of an AFX zeolite and a BEA-type zeolite, and containing copper, at a content of between 0.05 and 6% by weight, preferably between 0.5 and 0.5% by weight. and 5% by weight, and more preferably between 1 and 4% by weight, based on the total weight of said catalyst in its anhydrous form, said catalyst having a zeolite structure comprising:

16. Catalyst according to claim 15, containing only copper as a transition metal and wherein the total mass content of copper is between 0.5 to 6% by weight, preferably between 0.5 and 5%, preferably between 1 and 5%. and 4% and more preferably between 1.5% and 3.5%, based on the total weight of the anhydrous final catalyst.

17. A catalyst according to claim 15, containing copper and another transition metal and wherein the copper content is between 0.05 and 2% by weight, preferably 0.5 and 2% by weight, while the content of the other transition metal is preferably between 1 and 4% by weight, the content of transition metals being given as a percentage by weight relative to the total weight of the anhydrous final catalyst.

18. Catalyst according to one of claims 15 to 17, obtainable or obtained directly by the method according to one of claims 1 to 14.

19. Use of the catalyst according to one of claims 15 to 18 or prepared by the method according to any one of claims 1 to 14, for the selective reduction of NO _x by a reducing agent such as NH ₃ or H ₂ .

20. Use according to the preceding claim, wherein the catalyst is shaped by deposition in the form of a coating on a monolith, preferably a honeycomb structure or a plate structure.

21. Use according to claim 20, wherein the honeycomb structure is formed of parallel channels open at both ends or comprises porous filtering walls for which the adjacent parallel channels are alternately plugged on either side of the channels.

22. Use according to claim 21, wherein the amount of catalyst deposited on said structure is between 50 to 180 g / l for the filter structures and between 80 and 200 g / l for open channel structures.

23. Use according to one of claims 19 to 22, wherein said catalyst is associated with a binder such as ceria, zirconium oxide, alumina, non-zeolitic silica-alumina, titanium oxide, a mixed ceria-zirconia type oxide, a tungsten oxide and / or a spinel, to be shaped by coating deposition.

24. Use according to one of claims 19 to 23, wherein said coating is associated with another coating having pollutant adsorption capabilities in particular NOx, pollutants reduction especially NOx or promoting oxidation of pollutants.

25. Use according to claim 19, wherein said catalyst is in extruded form, containing up to 100% of said catalyst.

26. Use according to one of claims 19 to 25, wherein the structure coated by said catalyst or obtained by extrusion of said catalyst is integrated in an exhaust line of an internal combustion engine.