JP2021524373A - A catalyst containing a very high purity AFX-structured zeolite and at least one transition metal for the selective reduction of NOx. - Google Patents

Abstract

The present invention relates to methods for preparing catalysts based on very pure AFX-structured zeolites and at least one transition metal, comprising at least the following steps: i) 6.0-200 (limits) in an aqueous medium. A FAU-structured zeolite having a SiO2 (FAU) / Al2O3 (FAU) molar ratio of (including values), an organic nitrogen compound R, and at least one source of at least one alkali and / or alkaline earth metal M. Mix until a homogeneous precursor gel is obtained; ii) hydrothermal treatment of the precursor gel to obtain a solid crystalline phase, i.e. "solid"; iii) at least one ion exchange with a transition metal; iv) heat treatment. The present invention also relates to catalysts that can be obtained or obtained directly by this method, and their use for selective NOx reduction. [Selection diagram] Fig. 3

Description

The subject of the present invention is a method for preparing a catalyst based on an AFX-structured zeolite and at least one transition metal, in the presence of a catalyst prepared or can be prepared by the method, and a reducing agent. Its use, especially for the selective catalytic reduction of NOx in internal combustion engines.

Emissions of nitrogen oxides (NOx) generated by burning fossil fuels are of great concern to society. Increasingly stringent standards are being set by government authorities to limit the environmental and health impacts of combustion emissions. In Europe, light vehicles must not exceed very low levels of NOx and particle emissions under all operating conditions under the Euro 6c standard. The new WLTC test cycle (World Harmonized Light Vehicles Test Cycle) and the regulation of actual driving emissions (RDE) combined with compliance factors require the development of highly effective emission control systems to meet these goals. And. Selective catalytic reduction (SCR) has emerged as an effective technique for removing nitrogen oxides from oxygen-rich exhaust gases typical of diesel and positive ignition engines in lean air-fuel mixture mode. Selective catalytic reduction, a reducing agent, typically carried out using ammonia and can therefore be referred to as NH ₃ -SCR. _{Ammonia (NH 3} ) involved in the SCR process is usually produced through the decomposition of an aqueous urea solution (AdBlue or DEF) and when it reacts with NOx, it produces N ₂ and H ₂ O.

Zeolites exchanged for transition metals are used as catalysts _{, especially for NH 3-SCR applications in transport.} Small pore zeolites, especially copper exchange chabazite, are particularly suitable. They are commercially available in the form of silico-aluminophosphate Cu-SAPO-34 and aluminosilicate Cu-SSZ-13 (or Cu-SSZ-62). Their water heat resistance and NOx conversion efficiency are the current standards. However, as regulations become more and more restrictive, catalyst performance needs to be further improved.

Although the _{use of AFX-structured zeolites for NH 3-} SCR applications is known, few studies have evaluated the effectiveness of catalysts using this zeolite.

Fickel et al. (Fickel, DW & Lobo, RF (2009), The Journal of Physical Chemistry C, 114 (3), 1633-1640) use copper exchange SSZ-16 (having an AFX structure) for NOx removal. I am studying. This zeolite is synthesized according to Japanese Patent US5194235, and copper is introduced by exchange with copper (II) sulfate for 1 hour at 80 ° C. Recent results (Fickel, DW, D'Addio, E., Waterproof, JA, & Lobo, RF (2011), 102 (3), 441-448) show that for a 3.78 mass% copper load. It showed excellent conversion rate and good water heat resistance.

Studies on the synthesis of AFX-structured zeolites include synthetic optimization studies (Hrabanek, P., Zikanova, A., Supinkova, T., Drahokoupil, J., Fila, V., Lhotka, M., Bernauer, B. (2016). ), Microporous and Optimize Materials, 228, 107-115), as well as various structuring agents (Lobo, RF, Zones, SI, & Medrud, RC (1996), Chemistry of Materials, 8 (10), 2409). It is done about 2411).

Wang et al. (Wang, D. et al., CrystEngComm., (2016), 18 (6), 1000-1008) replace the TMHD structuring agent with a TEA-TMA mixture for the formation of SAPO-56. This was studied to obtain the undesired SAPO-34 and SAPO-20 phases. Incorporation of transition metals has not been discussed.

Patent US2016 / 0137518 is a semi-pure AFX zeolite, its synthesis from silica and alumina sources in the presence of 1,3-bis (1-adamantyl) imidazolium hydroxide structuring agent, AFX exchanged with transition metals. The preparation of zeolite-based catalysts, as well _{as their use for NH 3-} SCR applications, is described. No special form of AFX zeolite is mentioned.

More recently, the patent US2018 / 093259 has issued small amounts such as AFX-structured zeolites from FAU-type zeolites in the presence of structuring agents such as 1,3-bis (1-adamantyl) imidazolium hydroxide and alkaline earth metal sources. Describes the synthesis of pore zeolite. It also describes the application of the resulting AFX-structured zeolite, in particular the use of this zeolite as a NOx reduction catalyst, followed by its replacement with a metal such as iron. In parallel, the patent US2016 / 0996169A1 describes the use of a catalyst based on an AFX-structured zeolite having a Si / Al ratio of 15-50 metal exchanged in NOx conversion, wherein the AFX zeolite is 1,3-bis. It is obtained starting from the (1-adamantyl) imidazolium hydroxide structuring agent. The results obtained with the NOx conversion show, in particular, the selectivity of the catalysts prepared according to patents US2018 / 093259 and patents US2016 / 0996169 to nitrous oxide not exceeding 20 ppm.

JP2014-148441 describes the synthesis of solids for AFX zeolites, especially copper-containing SAPO-56, that can be used for NOx reduction. The solid is synthesized and then added to the mixture containing alcohol and copper salts and the entire mixture is calcined. Thus, copper is added after the formation of the SAPO solid for the AFX-structured zeolite. This exchanged solid appears to have increased resistance to the presence of water.

Ogura et al. (Bull. Chem. Soc. Jpn., 2018, 91, 355-361) found that the copper exchange SSZ-16 zeolite had very good activity compared to other zeolite structures, even after hydrothermal aging. Is demonstrating.

WO2017 / 080722 discloses the direct synthesis of copper-containing zeolites. This synthesis requires the use of _{TEPA complexing agents and M (OH) X} molecules, starting with FAU-structured zeolites, to obtain various types, primarily CHA-type zeolites. ANA, ABW, PHI and GME type zeolites are also produced.

Applicant has specific synthetic methods AFX structure prepared according zeolite and at least one transition metal, the catalyst is particularly based on copper, it was found to exhibit an interesting result with respect selectivity to NOx conversion and N _{2 O.} Especially, the results of the NOx conversion, particularly in a low temperature (T <250 ℃), and better than those obtained by prior art catalysts, such as catalysts based on copper exchanged AFX structured zeolite, the nitrous oxide N _{2 O} at the same time Good selectivity of is maintained.

U.S. Patent Application Publication No. 2016/0137518 U.S. Patent Application Publication No. 2018/093259 U.S. Patent Application Publication No. 2016/096169 Japanese Unexamined Patent Publication No. 2014-148441 International Publication No. 2017/080722

Fickel, DW & Lobo, RF, The Journal of Physical Chemistry C, 2009, 114 (3), 1633-1640 Fickel, DW, D'Addio, E.I. , Laterbach, JA, & Lobo, RF, 2011,102 (3), 441-448 Hrabanek, P. et al. , Zikanova, A.I. , Supinkova, T. et al. , Drahokoupil, J. Mol. , Fila, V.I. , Lhotka, M. et al. , Bernauer, B.I. , Microporous and Mesoporous Materials, 2016, 228, 107-115 Lobo, RF, Zones, SI, & Medrud, RC, Chemistry of Materials, 1996, 8 (10), 2409-2411 Wang, D. et al. , CrystEngComm. , 2016, 18 (6), 1000-1008 Bull. Chem. Soc. Jpn. , 2018, 91, 355-361

The present invention relates to a method for preparing a catalyst based on an AFX-structured zeolite and at least one transition metal, which comprises at least the following steps:
_{i) In an aqueous medium, a FAU-structured zeolite having a SiO 2 (FAU)} / Al ₂ O _{3 (FAU)} molar ratio of 6.0 to 200 (including the limit value) and an organic nitrogen compound R (R is 1). , 5-Bis (Methylpiperidinium) Pentane Dihydroxydo, 1,6-bis (Methylpiperidinium) Hexanedihydroxydo or 1,7-Bis (Methylpiperidinium) Heptanedihydroxydo), At least one alkali and / or alkaline earth metal with a valence of n At least one source of M (n is an integer greater than or equal to 1 and M is lithium, potassium, sodium, magnesium and calcium, and of these metals. (Choose from at least two mixtures) and is mixed until a homogeneous precursor gel is obtained.
The reaction mixture has the following molar composition:
(SiO _{2 (FAU)} ) / (Al ₂ O _{3 (FAU)} ) is 6.0 to 200, preferably 6.0 to 100,
H ₂ O / (SiO _{2 (FAU)} ) is 1.00 to 100, preferably 5 to 60,
R / (SiO _{2 (FAU)} ) is 0.01 to 0.60, preferably 0.05 to 0.50.
M _{2 / n} O / (SiO _{2 (FAU)} ) is 0.005 to 0.45, preferably 0.05 to 0.25.
However, including the limit value,
_{Here, SiO 2 (FAU)} indicates the amount of SiO ₂ provided by the FAU _zeolites, Al _{2 O 3 (FAU)} indicates the amount of _Al 2 _{O 3} which is provided by the FAU zeolite;
ii) Hydrothermal treatment of the precursor gel obtained at the end of step i) for 12 hours to 15 days at a temperature of 120 ° C to 220 ° C to obtain a solid crystalline phase, i.e. "solid";
iii) The solid obtained at the end of the previous step is stirred at room temperature for 1 hour to 2 days to release at least one species capable of releasing transition metals, especially copper, in a solution in reactive form. At least one ion exchange, including contacting with the containing solution;
iv) Heat treatment by drying the solid obtained at the end of the previous step at a temperature of 20 to 150 ° C., and then firing at least once at a temperature of 400 to 700 ° C. under air flow.

Steps iii) and iv) can be reversed and may be repeated arbitrarily.

The reaction mixture of step i) _{can include at least one additional source of XO 2} oxide, where X is one or more selected from the group formed by the following elements: silicon, germanium, titanium: It is a tetravalent element and has a XO ₂ / SiO _{2 (FAU)} molar ratio of 0.001 to 1, preferably 0.001 to 0.9, more preferably 0.001 to 0.01, provided that the limit value. _{The SiO 2 (FAU)} content in the above ratio is the content provided by the FAU-structured zeolite.

The reaction mixture of step i) advantageously has the following molar composition:
(XO ₂ + SiO _{2 (FAU)} ) / Al ₂ O _{3 (FAU)} is 6.0 to 200, preferably 6.0 to 100,
H ₂ O / (XO ₂ + SiO _{2 (FAU)} ) is 1 to 100, preferably 5 to 60.
R / (XO ₂ + SiO _{2 (FAU)} ) is 0.01 to 0.6, preferably 0.05 to 0.5,
M _{2 / n} O / (XO ₂ + SiO _{2 (FAU)} ) is 0.005 to 0.45, preferably 0.05 to 0.25, but includes a limit value.

Preferably, X is silicon.

The reaction mixture of step i) _{can then include at least one additional source of Y 2} O ₃ oxide, where Y is selected from the group formed by the following elements: aluminum, boron, gallium: One or more trivalent elements with a Y ₂ O ₃ / Al ₂ O _{3 (FAU)} molar ratio of 0.001-10, preferably 0.001-8, but including limit values, said ratio. The Al ₂ O _{3 (FAU)} content in is the content provided by the FAU-structured zeolite.

The reaction mixture of step i) advantageously has the following molar composition:
SiO _{2 (FAU)} / (Al ₂ O _{3 (FAU)} + Y ₂ O ₃ ) is 6.0 to 200, preferably 6.0 to 100,
H ₂ O / SiO _{2 (FAU)} is 1-100, preferably 5-60,
R / SiO _{2 (FAU)} is 0.01 to 0.6, preferably 0.05 to 0.5,
M _{2 / n} O / SiO _{2 (FAU)} is 0.005 to 0.45, preferably 0.05 to 0.25.
However, including the limit value
SiO _{2 (FAU)} is the amount of _{SiO 2} provided by the FAU zeolite _{, and Al 2} O _{3 (FAU)} is the amount of _{Al 2} O ₃ provided by the FAU zeolite.

Preferably, Y is aluminum.

The reaction mixture of step i) is
-At _{least one additional source of XO 2} oxide-and at least one additional source of Y ₂ O ₃ oxide can be included.
The FAU zeolite is 5 to 95% by mass, preferably 50, based on the total amount of the trivalent and tetravalent elements SiO _{2 (FAU)} , XO ₂ , Al ₂ O _{3 (FAU)} and Y ₂ O _{3 in the reaction mixture.} It accounts for ~ 95% by weight, very preferably 60-90% by weight, even more preferably 65-85% by weight, and the reaction mixture has the following molar composition:
(XO ₂ + SiO _{2 (FAU)} ) / (Al ₂ O _{3 (FAU)} + Y ₂ O ₃ ) is 6.0 to 200, preferably 6.0 to 100,
H ₂ O / (XO ₂ + SiO _{2 (FAU)} ) is 1 to 100, preferably 5 to 60.
R / (XO ₂ + SiO _{2 (FAU)} ) is 0.01 to 0.6, preferably 0.05 to 0.5,
M _{2 / n} O / (XO ₂ + SiO _{2 (FAU)} ) is 0.005 to 0.45, preferably 0.05 to 0.25, but includes a limit value.

Advantageously, the molar ratio of the total amount represented as the oxide of the tetravalent element to the total amount represented as the oxide of the trivalent element of the precursor gel obtained at the end of step i) is 6.00 to 100. Yes, but includes limits.

The FAU-structured zeolite preferably has a SiO ₂ / Al ₂ O ₃ molar ratio of 6.0 to 100, but contains a limit value.

The seed crystal of the AFX structure zeolite is preferably 0.01 to 10% by mass based on the total mass of the anhydrous tetravalent and trivalent element present in the reaction mixture of step i). Seed crystals are not considered in the total mass of the source of tetravalent and trivalent elements.

Step i) may include aging the reaction mixture at a temperature of 20-100 ° C. for 30 minutes-48 hours with or without stirring.

The hydrothermal treatment of step ii) can be carried out at a temperature of 120 ° C. to 220 ° C., preferably 150 ° C. to 195 ° C., for 12 hours to 12 days, preferably 12 hours to 10 days under self-sustaining pressure.

The ion exchange step iii) involves contacting the solid with a solution containing only one species capable of releasing the transition metal, or at least one, preferably only one, each capable of releasing the transition metal. It can be carried out by continuous contact of the solid with various solutions containing seeds, and the transition metals of the various solutions are preferably different from each other.

The at least one transition metal released into the exchange solution of step iii) is formed from the following elements: Ti, V, Mn, Mo, Fe, Co, Cu, Cr, Zn, Nb, Ce, Group formed from Zr, Rh, Pd, Pt, Au, W, Ag, preferably the following elements: Select from the group formed from Fe, Cu, Nb, Ce or Mn, more preferably Fe or Cu. And even more preferably, the transition metal is Cu.

The content of the transition metal introduced by the ion exchange step iii) is preferably 0.5 to 6% by mass, preferably 0.5 to 5% by mass, more preferably, based on the total mass of the final anhydrous catalyst. It is 1 to 4% by mass.

Advantageously, the heat treatment step iv) dries the solid at a temperature of 20 to 150 ° C., preferably 60 to 100 ° C. for 2 to 24 hours, followed by air, optionally in dry air, 450 to 700 ° C. The flow rate of any dry air is preferably 0.5 to 1. 1. It comprises firing at least once at 5 L / h / g, more preferably 0.7-1.2 L / h / g of the solid being treated.

The present invention also relates to catalysts based on AFX zeolites and at least one transition metal that can be obtained or obtained directly by the preparation method.

The transition metal is a group formed from the following elements: Ti, V, Mn, Mo, Fe, Co, Cu, Cr, Zn, Nb, Ce, Zr, Rh, Pd, Pt, Au, W, Ag, preferably Can be selected from the group formed from the following elements: Fe, Cu, Nb, Ce or Mn, more preferably from the group formed from Fe or Cu, and even more preferably the transition metal is Cu. ..

The total content of the transition metal is preferably 0.5 to 6% by mass, preferably 0.5 to 5% by mass, and more preferably 1 to 4% by mass with respect to the total mass of the final anhydrous catalyst.

In one embodiment, the catalyst contains only copper, the content of which is 0.5 to 6% by weight, preferably 0.5 to 5% by weight, more preferably 1 to 4 relative to the total mass of the final anhydrous catalyst. It is mass%.

In another embodiment, the catalyst comprises copper in combination with at least one other transition metal selected from the group formed from Fe, Nb, Ce, Mn, the content of copper in the catalyst being final anhydrous. It is 0.05 to 2% by mass, preferably 0.5 to 2% by mass, based on the total mass of the catalyst, and the content of the at least one other transition metal is based on the total mass of the final anhydrous catalyst. It is 1 to 4% by mass.

In yet another embodiment, the catalyst comprises iron in combination with other metals selected from the group formed from Cu, Nb, Ce, Mn and the iron content is relative to the total mass of the final anhydrous catalyst. The content of the other transition metal is 0.05 to 2% by mass, preferably 0.5 to 2% by mass, and the content of the other transition metal is 1 to 4% by mass with respect to the total mass of the final anhydrous catalyst.

The present invention also relates to the use of the catalysts described above, or the use of catalysts that can be obtained or obtained directly by the preparation method, for the selective reduction of NOx with a reducing agent such as _{NH 3} or H _2.

The catalyst can be formed by depositing in the form of a coating on a honeycomb structure or plate structure.

The honeycomb structure may be formed by parallel grooves that are open at both ends, or may include a porous filtration wall, in which adjacent parallel grooves are alternately blocked at both ends of the groove.

The amount of catalyst deposited on the structure is advantageously 50-180 g / L for filtration structures and 80-200 g / L for structures with open grooves.

The catalyst is formed by deposition in the form of a coating, such as celine, zirconium oxide, alumina, non-zeolite silica-alumina, titanium oxide, serine-zirconia mixed oxide, tungsten oxide and / or spinel. Can be combined with a binder.

The coating can be combined with other coatings capable of adsorbing contaminants, especially NOx, reducing contaminants, especially NOx, or promoting oxidation of contaminants.

The catalyst may be in the form of an extrude containing up to 100% of the catalyst.

Structures coated with the catalyst or obtained by extrusion of the catalyst may be incorporated into the exhaust line of an internal combustion engine.

FIG. 1 represents a chemical formula of an organic nitrogen compound that can be selected as a structuring agent used in the synthetic method according to the present invention. FIG. 2 shows an X-ray diffraction pattern of the AFX zeolite obtained according to Example 2. FIG. 3 is according to Example 2 (CuAFX3, curve represented by a square according to the present invention), Example 3 (CuAFX1, curve represented by a circle according to the present invention) and Example 4 (CuSSZ16, comparative, curve represented by a triangle). The synthesized catalyst was obtained in a catalytic test on the reduction of nitrogen oxides (NOx) by ammonia (NH _{3 ) in the presence of oxygen (O 2} ) as a function of temperature T ° C. under standard SCR conditions. It represents the conversion rate C (%). FIG. 4 shows according to Example 2 (CuAFX3, curve represented by a square according to the present invention), Example 3 (CuAFX1, curve represented by a circle according to the present invention) and Example 4 (CuSSZ16, comparative, curve represented by a triangle). The synthesized catalyst was obtained in a catalytic test on the reduction of nitrogen oxides (NOx) by ammonia (NH _{3 ) in the presence of oxygen (O 2} ) as a function of temperature T ° C. under high speed SCR conditions. It represents the conversion rate C (%). FIG. 5 shows the catalysts (CuAFX3aged, according to the invention, triangular, and CuSSZ16aged, comparative, circled) synthesized according to Examples 2 and 4 and then aged by the method described in Example 5. Obtained in a catalytic test on the reduction of nitrogen oxides (NOx) by ammonia (NH _{3 ) in the presence of oxygen (O 2} ) as a function of temperature T ° C. under standard SCR conditions after hydrothermal aging. It represents the conversion rate C (%).

Other features and advantages of the synthetic methods according to the invention, the catalysts according to the invention, and their use according to the invention are provided in a non-limiting exemplary practice with reference to the accompanying drawings described below. It will become clear by reading the following description of the morphology.

Detailed Description of the Invention The present invention relates to a method for preparing a catalyst containing an AFX-structured zeolite and at least one transition metal, which comprises at least the following steps:
i) in an aqueous medium, from 6 to 200 (the FAU structure zeolite having a _{SiO 2 (FAU) / Al 2} O 3 (FAU) molar ratio limits included), 1,5-bis (methylpiperidinium) With an organic nitrogen compound R selected from pentanedihydroxydo, 1,6-bis (methylpiperidinium) hexanedihydroxydo, or 1,7-bis (methylpiperidinium) heptanedihydroxydo, also called a specific structuring agent. , At least one alkali and / or alkaline earth metal M with a valence of n (n is an integer greater than or equal to 1 and M is from lithium, potassium, sodium, magnesium and calcium, and at least two mixtures of these metals. (Selected), and the mixture has the following molar composition:
(SiO _{2 (FAU)} ) / (Al ₂ O _{3 (FAU)} ) is 6.0 to 200, preferably 6.0 to 100,
H ₂ O / (SiO _{2 (FAU)} ) is 1 to 100, preferably 5 to 60,
R / (SiO _{2 (FAU)} ) is 0.01 to 0.6, preferably 0.05 to 0.5,
M _{2 / n} O / (SiO _{2 (FAU)} ) is 0.005 to 0.45, preferably 0.05 to 0.25.
_{Here, SiO 2 (FAU)} indicates the amount of SiO ₂ provided by the FAU _zeolites, Al _{2 O 3 (FAU)} shows the amount of _Al 2 _{O 3} which is provided by the FAU _{zeolites, H} 2 O Is the molar amount of water present in the reaction mixture, R is the molar amount of the organic nitrogen compound, and M _{2 / n} O is provided by the source of the alkali metal and / or alkaline earth metal. A molar amount expressed in the form of an M _{2 / n} O oxide, where M is one or more alkalis selected from at least two mixtures of lithium, sodium, potassium, calcium, magnesium and metals thereof. / Or an alkaline earth metal, very preferably M is sodium, and step i) is carried out over a period of time that makes it possible to obtain a homogeneous mixture known as the precursor gel;
ii) Hydrothermal treatment of the precursor gel obtained at the end of step i) for 12 hours to 15 days at a temperature of 120 ° C to 220 ° C to obtain a solid crystalline phase, i.e. "solid";
iii) The solid obtained at the end of the previous step contains at least one species capable of releasing transition metals, especially copper, in a solution in reactive form with stirring at room temperature for 1 hour to 2 days. At least one ion exchange, including contact with a solution;
iv) Heat treatment by drying the solid obtained at the end of the previous step at a temperature of 20-150 ° C and then firing at least once at a temperature of 400-700 ° C under air flow;
Advantageously, steps iii) and iv) can be reversed and optionally repeated if necessary.

The present invention also relates to catalysts comprising AFX-structured zeolites and at least one transition metal, which can be obtained by the methods described above or can be obtained directly.

Finally, the present invention relates to the use of the catalyst according to the present invention for the selective catalytic reduction of NOx in the presence of a reducing agent.

Catalysts The catalyst according to the invention comprises at least one AFX-type catalyst and at least one additional transition metal, preferably copper.

According to the present invention, the transition metal contained in the catalyst is selected from the group of elements formed from the elements of Groups 3 to 12 of the Periodic Table of the Elements, including lanthanide.

In particular, the transition metal contained in the catalyst is selected from the group formed from the following elements: Ti, V, Mn, Mo, Fe, Co, Cu, Cr, Zn, Nb, Ce, Zr, Rh, Pd, Pt, Au, W, Ag.

Preferably, the catalyst according to the invention comprises copper alone or in combination with a group of elements listed above, in particular at least one other transition metal selected from Fe, Nb, Ce, Mn.

The total content of the transition metal is 0.5 to 6% by weight, preferably 0.5 to 5% by weight, even more preferably 1 to 4% by weight, based on the total weight of the final catalyst in its anhydrous form. ..

In the case of a catalyst containing only copper as a transition metal, the content thereof is 0.5 to 6% by mass, preferably 0.5 to 5% by mass, and more preferably 1 to 1% with respect to the total mass of the final anhydrous catalyst. It is 4% by mass.

For catalysts containing copper and other elements, such as Fe, Nb, Ce, Mn, the catalyst has a copper content of 0.05-2% by mass, preferably 0.5-2% by mass. The content of the other transition metals is preferably 1 to 4% by mass, and the content of the transition metals is given as a mass ratio to the total mass of the final drying catalyst.

In the case of a catalyst containing only iron as a transition metal, the content thereof is 0.5 to 4% by mass, and even more preferably 1.5 to 3.5% by mass, based on the total mass of the final anhydrous catalyst. ..

For catalysts containing iron and other elements, such as preferably Cu, Nb, Ce, Mn, the iron content of the catalyst is 0.05-2% by mass, preferably 0.5-2% by mass. The content of the other transition metals is preferably 1 to 4% by mass, and the content of the transition metals is given as a mass ratio to the total mass of the final drying catalyst.

The catalyst according to the present invention further contains other elements, such as alkali and / or alkaline earth metals, such as sodium, which are derived in particular from the synthesis, especially the synthesis of the reaction medium compound in step i) of the method for preparing the catalyst. You may be doing it.

Preparation method of catalyst Mixing step i)
Step i) includes:
i) in an aqueous medium, from 6 to 200 (the FAU structure zeolite having a _{SiO 2 (FAU) / Al 2} O 3 (FAU) molar ratio limits included), 1,5-bis (methylpiperidinium) With an organic nitrogen compound R selected from pentane dihydroxydo, 1,6-bis (methylpiperidinium) hexanedihydroxydo, or 1,7-bis (methylpiperidinium) heptanedihydroxydo, also called a specific structuring agent. , At least one alkali metal and / or alkaline earth metal M having a valence of n (n is an integer of 1 or more) is mixed, and the mixture has the following molar composition:
(SiO _{2 (FAU)} ) / (Al ₂ O _{3 (FAU)} ) is 6.0 to 200, preferably 6.0 to 100,
H ₂ O / (SiO _{2 (FAU)} ) is 1 to 100, preferably 5 to 60,
R / (SiO _{2 (FAU)} ) is 0.01 to 0.6, preferably 0.05 to 0.50,
M _{2 / n} O / (SiO _{2 (FAU)} ) is 0.005 to 0.45, preferably 0.05 to 0.25.
Here, SiO _{2 (FAU)} is the amount of _{SiO 2} provided by the FAU zeolite _{, and Al 2} O _{3 (FAU)} is the amount of _{Al 2} O ₃ provided by the FAU zeolite _{, H 2} O. Is the molar amount of water present in the reaction mixture, R is the molar amount of the organic nitrogen compound, and M _{2 / n} O is provided by the source of the alkali metal and / or alkaline earth metal. A molar amount expressed in the form of an M _{2 / n} O oxide, where M is one or more alkalis selected from at least two mixtures of lithium, sodium, potassium, calcium, magnesium and metals thereof. / Or an alkaline earth metal, very preferably M is sodium, and step i) is carried out over a period of time that allows to obtain a homogeneous mixture known as the precursor gel.

_{The starting material FAU-structured zeolites having a SiO 2} / Al ₂ O ₃ molar ratio of 6 to 200 (including limit values) can be prepared by any method known to those skilled in the art, such as SiO ₂ / Al _{2 less than 6.00.} O ₃ molar ratio can be obtained by steam treatment (steaming) and acid washing on the FAU structure zeolite with. As FAU source having 6.00 or more of _SiO 2 / _Al 2 _{O 3} ratio, a commercially available zeolite produced by Zeolyst CBV712, CBV720, CBV760 and CBV780, and commercial zeolite HSZ-350HUA, manufactured by TOSOH, HSZ- Included are 360 HUA and HSZ-385 HUA.

As described above, in the preparation method according to the present invention, the SiO ₂ / Al ₂ O ₃ ratio of the precursor gel containing the FAU structure zeolite is adjusted to at least 1 of the selected FAU structure zeolite and at least one tetravalent element XO ₂ . It is possible to adjust according to the presence or absence of further supply of one source and / or at least one source of at least one trivalent element Y ₂ O _{3 in the reaction mixture.}

_{In step i), a FAU-structured zeolite having a SiO 2} / Al ₂ O _{3 (FAU)} molar ratio of 6 to 200 (including a limit value) and an organic nitrogen compound R (R is 1,5) in an aqueous medium are used. -Bis (methylpiperidinium) pentanehydroxydide, 1,6-bis (methylpiperidinium) hexanedihydroxydo, or 1,7-bis (methylpiperidinium) heptanedihydroxydo, alone or as a mixture. Used) and at least one alkali metal and / or alkaline earth metal M with a valence of n (n is an integer greater than or equal to 1), and the reaction mixture comprises the following molar composition: Have:
(SiO _{2 (FAU)} ) / (Al ₂ O _{3 (FAU)} ) is 6.0 to 200, preferably 6.0 to 100,
H ₂ O / (SiO _{2 (FAU)} ) is 1 to 100, preferably 5 to 60,
R / (SiO _{2 (FAU)} ) is 0.01 to 0.6, preferably 0.05 to 0.5,
M _{2 / n} O / (SiO _{2 (FAU)} ) is 0.005 to 0.45, preferably 0.05 to 0.25.
Here, SiO _{2 (FAU)} is the amount of _{SiO 2} provided by FAU zeolite _{, Al 2} O _{3 (FAU) is the amount of Al 2} O ₃ provided by FAU zeolite, and M is. One or more alkali and / or alkaline earth metals selected from lithium, sodium, potassium, calcium, magnesium and at least two mixtures of these metals, with very preferred M being sodium.

In a preferred embodiment, the reaction mixture of step i) comprises at least one additional source of _{XO 2 oxide, with a XO 2} / SiO _{2 (FAU)} molar ratio of 0.001 to 1, and the mixture is advantageous. Has the following molar composition:
(XO ₂ + SiO _{2 (FAU)} ) / Al ₂ O _{3 (FAU)} is 6.0 to 200, preferably 6.0 to 100,
H ₂ O / (XO ₂ + SiO _{2 (FAU)} ) is 1 to 100, preferably 5 to 60.
R / (XO ₂ + SiO _{2 (FAU)} ) is 0.01 to 0.6, preferably 0.05 to 0.5,
M _{2 / n} O / (XO ₂ + SiO _{2 (FAU)} ) is 0.005 to 0.45, preferably 0.05 to 0.25.
Here, X is one or more tetravalent elements selected from the group formed by the following elements: silicon, germanium, and titanium, X is preferably silicon, and SiO _{2 (FAU)} is FAU. The content of _{SiO 2} provided by zeolite _{, Al 2} O _{3 (FAU) is the content of Al 2} O ₃ provided by FAU zeolite, and R is 1,5-bis (methyl piperidi). Nium) pentandihydroxydo, 1,6-bis (methylpiperidinium) hexanedihydroxydo or 1,7-bis (methylpiperidinium) heptanedihydroxydo, where M is lithium, sodium, potassium, calcium, magnesium. And one or more alkali and / or alkaline earth metals selected from at least two mixtures of these metals, M being very preferably sodium.

In another preferred embodiment, the reaction mixture of step i) also comprises at least one additional source of _{Y 2} O _{3 oxide with a Y 2} O ₃ / Al ₂ O _{3 (FAU)} molar ratio of 0.001- At 10, the mixture advantageously has the following molar composition:
SiO _{2 (FAU)} / (Al ₂ O _{3 (FAU)} + Y ₂ O ₃ ) is 6.0 to 200, preferably 6.0 to 100,
H ₂ O / SiO _{2 (FAU)} is 1-100, preferably 5-60,
R / SiO _{2 (FAU)} is 0.01 to 0.6, preferably 0.05 to 0.5,
M _{2 / n} O / SiO _{2 (FAU)} is 0.005 to 0.45, preferably 0.05 to 0.25.
Here, Y is one or more trivalent elements selected from the group formed by the following elements: aluminum, boron, gallium, Y is preferably aluminum, and SiO _{2 (FAU)} is FAU zeolite. Is the amount of _{SiO 2} provided by _{FAU, Al 2} O _{3 (FAU) is the amount of Al 2} O ₃ provided by FAU zeolite, and R is 1,5-bis (methylpiperidinium) pentane. Dihydroxydo, 1,6-bis (methylpiperidinium) hexanedihydroxydo or 1,7-bis (methylpiperidinium) heptanedihydroxydo, where M is lithium, sodium, potassium, calcium, magnesium and these. One or more alkaline and / or alkaline earth metals selected from at least two mixtures of metals, where M is very preferably sodium.

In another preferred embodiment, the reaction mixture of step i) is 5 to 95% by weight, preferably 50 to 95% by weight, very preferably, based on the total amount of trivalent and tetravalent element sources in the mixture. It contains 60-90% by weight, even more preferably 65-85% by weight of FAU-structured zeolite, and further sources of at least one additional source of _{XO 2 oxide and at least one additional source of Y 2} O ₃ oxide. The reaction mixture has the following molar composition:
(XO ₂ + SiO _{2 (FAU)} ) / (Al ₂ O _{3 (FAU)} + Y ₂ O ₃ ) is 6.0 to 200, preferably 6.0 to 100,
H ₂ O / (XO ₂ + SiO _{2 (FAU)} ) is 1 to 100, preferably 5 to 60.
R / (XO ₂ + SiO _{2 (FAU)} ) is 0.01 to 0.6, preferably 0.05 to 0.5,
M _{2 / n} O / (XO ₂ + SiO _{2 (FAU)} ) is 0.005 to 0.45, preferably 0.05 to 0.25.
Here, X is one or more tetravalent elements selected from the group formed by the following elements: silicon, germanium, and titanium, X is preferably silicon, and Y is the following element: aluminum. , Boron, one or more trivalent elements selected from the group formed by gallium, Y is preferably aluminum, SiO _{2 (FAU)} is the amount of _{SiO 2} provided by FAU zeolite. Al ₂ O _{3 (FAU) is the amount of Al 2} O ₃ provided by the FAU zeolite, where R is 1,5-bis (methylpiperidinium) pentandihydroxyde, 1,6-bis (methylpi). Peridinium) hexanedihydroxydo or 1,7-bis (methylpiperidinium) heptanedihydroxyde, where M is selected from at least two mixtures of lithium, sodium, potassium, calcium, magnesium and these metals 1 More than one alkali and / or alkaline earth metal, M is very preferably sodium.

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

According to the present invention, a FAU-structured zeolite having _{a SiO 2 (FAU)} / Al ₂ O _{3 (FAU)} molar ratio of 6 to 200 (including the limit value), preferably 6.0 to 100 (including the limit value). Is incorporated into the reaction mixture for the implementation of step (i) as a source of silicon and aluminum elements.

According to the present invention, R is 1,5-bis (methylpiperidinium) pentanedihydroxydo, 1,6-bis (methylpiperidinium) hexanedihydroxydo or 1,7-bis (methylpiperidinium). An organic nitrogen compound selected from heptane dihydroxydos, which is incorporated into the reaction mixture as an organic structuring agent for the implementation of step (i). The anion associated with the quaternary ammonium cation present in the organically structured species for the synthesis of the AFX-structured zeolite according to the present invention is a hydroxide anion.

According to the present invention, at least one source of alkali and / or alkaline earth metal M having a valence of n is used in the reaction mixture of step i), where n is an integer greater than or equal to 1 and M. Is preferably selected from lithium, potassium, sodium, magnesium and calcium, and at least two mixtures of these metals. Very preferably, M is sodium.
The source of at least one alkali and / or alkaline earth metal M is preferably sodium hydroxide.

According to the present invention, _{at least one additional source of XO 2} oxide (X is one or more tetravalent elements selected from the group formed by the following elements: silicon, germanium, titanium, where X is , Preferably silicon, with an XO ₂ / SiO _{2 (FAU)} molar ratio of 0.001 to 1, preferably 0.001 to 0.9, more preferably 0.001 to 0.01, in the above ratio. SiO _{2 (FAU)} content is the content provided by the FAU-structured zeolite) is advantageously used in the reaction mixture of step i).
In particular, _{the addition of at least one additional source of XO 2} oxide makes it possible to adjust _{the XO 2} / Y ₂ O ₃ ratio of the AFX-structured zeolite precursor gel obtained at the end of step i). do.

The source of the tetravalent element may be any compound containing the element X, which can be released in a reactive aqueous solution.
When X is titanium, Ti (EtO) ₄ is advantageously used as a titanium source.
Where X is preferably silicon, the silicon source is any one of the sources commonly used for zeolite synthesis, such as powdered silica, silicic acid, colloidal silica, dissolved silica or tetraethoxysilane (TEOS). It may be there. Among the powdered silicas, precipitated silicas, particularly those obtained by precipitation from solutions of alkali metal silicates, fumed silicas such as Cab-O-Sil and silica gel, can be used. Colloidal silica having various particle sizes, for example, average equivalent diameters of 10 to 15 nm or 40 to 50 nm, such as those sold under registered trade names such as Ludox, can be used. Preferably, the source of silicon is Cab-O-Sil.

According to the present invention, _{at least one additional source of Y 2} O ₃ oxide (Y is one or more trivalent elements selected from the group formed from the following elements: aluminum, boron, gallium): Is advantageously used in the mixture of step i). Preferably, Y is aluminum and the Y ₂ O ₃ / Al ₂ O _{3 (FAU)} molar ratio is 0.001 to 10, preferably 0.001 to 8, and Al ₂ O _{3 (in the above ratio). The FAU)} content is the content provided by the FAU-structured zeolite.
In this way, _{the XO 2} / Y ₂ O ₃ ratio of the AFX-structured zeolite precursor gel obtained at the end of step i) _{is adjusted by adding at least one additional source of Y 2} O _{3 oxide.} It becomes possible to do.

The source of the trivalent element Y may be any compound containing the element Y, and the element can be released in an aqueous solution in a reactive form. The element Y may be incorporated into the mixture in oxidized form YO _b (where 1 ≦ b ≦ 3, b is an integer or a rational number), or in any other form. Where Y is preferably aluminum, the aluminum source is preferably aluminum hydroxide or an aluminum salt such as chloride, nitrate or sulfate, sodium aluminate, aluminum alkoxide, or alumina itself, preferably hydrated or water. Compatible forms such as colloidal alumina, pseudo-bemite, γ-alumina or α or β-trihydrate. A mixture of the above sources can also be used.

Step (i) of the method according to the invention comprises a FAU-structured zeolite, optionally an XO ₂ or Y ₂ O ₃ oxide source, and at least one organic nitrogen compound R (R is 1,5-bis (R). An aqueous reaction mixture containing (selected from methylpiperidinium) pentanedihydroxydo, 1,6-bis (methylpiperidinium) hexanedihydroxydo or 1,7-bis (methylpiperidinium) heptanedihydroxydo). It consists of preparing in the presence of at least one source of one or more alkali metals and / or alkaline earth metals to obtain a precursor gel of AFX-structured zeolite. The amount of the reagent is adjusted in the manner described above to give the gel a composition that allows the AFX-structured zeolite to crystallize.

In order to reduce the time required for crystal formation of AFX-structured zeolite and / or total crystallization time, it is possible to add AFX-structured zeolite seeds to the reaction mixture during the step i) of the method of the present invention. Can be advantageous. The seed crystal also promotes the formation of the AFX-structured zeolite, which impairs impurities. Such species include crystals of crystalline solids, especially AFX-structured zeolites. Seed crystals are generally added at a ratio of 0.01% to 10% of the total anhydrous mass of the tetravalent and trivalent element sources used in the reaction mixture, and the seed crystals are tetravalent and trivalent. Not considered in the total mass of the elemental source. The species is not considered to determine the composition of the reaction mixture and / or gel as defined above, i.e. in determining the various molar ratios of the composition of the reaction mixture.

The mixing step i) is carried out for a time of preferably 15 minutes or more, preferably by any system known to those skilled in the art, with stirring at a low or high shear rate until a homogeneous mixture is obtained.
At the end of step i), a homogeneous precursor gel is obtained.

In order to control the crystal size of the AFX-structured zeolite, it may be advantageous to ripen the reaction mixture during the step i) of the method of the invention prior to hydrothermal crystallization. The aging also promotes the formation of the AFX-structured zeolite, which impairs impurities. The aging of the reaction mixture during said step i) of the method of the present invention can be carried out with or without stirring at room temperature or at a temperature of 20-100 ° C., advantageously for 30 minutes-48 hours. ..

Hydrothermal treatment step ii)
According to step ii) of the method according to the present invention, the precursor gel obtained at the end of step i) is preferably at 120 ° C. to 220 ° C. until the AFX-structured zeolite (or “crystalline solid”) is formed. It is subjected to a hydrothermal treatment performed at a temperature of ° C. for 12 hours to 15 days.
The precursor gel is preferably at 120 ° C. to 220 ° C., preferably at 150 ° C. to 195 ° C., with the addition of an optional gas, such as nitrogen, under self-sustaining pressure until the AFX-structured zeolite is completely crystallized. At the temperature of, it is placed under hydrothermal conditions.
The time required to obtain the crystals ranges from 12 hours to 15 days, preferably 12 hours to 12 days, more preferably 12 hours to 10 days.
The reaction is generally carried out with or without stirring, preferably with stirring. The agitation system that can be used is any system known to those of skill in the art, such as a tilted paddle with opposed wings, an agitation turbo mixer or an endless screw.

Very advantageously, the methods of the invention result in the formation of AFX-structured zeolites free of any other crystalline or amorphous phase.

Replacement process iii)
In the method for preparing the catalyst according to the present invention, the crystalline solid obtained at the end of the previous step, that is, the AFX zeolite obtained at the end of step ii), or the steps iii) and iv) are carried out in reverse. In a preferred case, the dried and calcined AFX zeolite obtained at the end of step iv) is stirred at room temperature for 1-2 days, preferably 0.5-1.5 days, in a reactive form of the solution. The transition metal can be released in the solution comprising at least one ion exchange step comprising contacting with at least one solution containing at least one species capable of releasing the transition metal, preferably copper. The resulting concentration of the species depends on the amount of transition metal incorporated into the crystalline solid.

It is also advantageous to obtain the protonated form of the AFX-structured zeolite after step ii). The hydrogen form can be obtained by performing ion exchange with an acid, particularly a strong mineral acid such as hydrochloric acid, sulfate or nitric acid, or a compound such as ammonium chloride, sulfate or nitrate, prior to ion exchange with the transition metal. Can be done.

The transition metals released into the exchange solution are selected from the group formed from the following elements: Ti, V, Mn, Mo, Fe, Co, Cu, Cr, Zn, Nb, Ce, Zr, Rh, Pd, Pt, Au, W, Ag. The transition metal is preferably Fe, Cu, Nb, Ce or Mn, preferably Cu.

According to the present invention, a "species capable of releasing a transition metal" is an organic metal of a species capable of dissociating in an aqueous medium, such as sulfates, nitrates, chlorides, oxalates, transition metals. It is understood to mean a complex, or a mixture thereof. Preferably, the species capable of releasing the transition metal is a sulfate or nitrate of the transition metal.

According to the present invention, a solution that contacts a crystalline solid or a dried and fired crystalline solid releases at least one species capable of releasing a transition metal, preferably a transition metal, preferably iron or copper. Contains only one species that can.

Advantageously, the method for preparing the catalyst according to the present invention is by contacting a solution containing a species capable of releasing a transition metal with a crystalline solid, or each of which releases a transition metal. It comprises a plurality of solutions containing possible species (various solutions include different species capable of releasing transition metals) and an ion exchange step iii by continuous contact of the solid.

At the end of the exchange, the resulting solid is advantageously filtered, washed and then dried to give the catalyst in powder form.

The total amount of the transition metal, preferably copper, contained in the final catalyst is 0.5 to 6% by mass with respect to the total mass of the catalyst in its anhydrous form.

According to one embodiment, the catalyst according to the invention is prepared by a method comprising an ion exchange step iii), the solid or the dried and fired solid releasing copper in solution in reactive form. Is contacted with a solution containing the seeds that form. Advantageously, the total amount of copper contained in the final catalyst, i.e. at the end of the preparation method according to the invention, is 0.5-6% by weight, preferably 1-6% by weight, with all proportions being the preparation method. It is a mass ratio to the total mass of the final catalyst according to the present invention in the anhydrous form obtained at the end of.

Heat treatment process iv)
The preparation method according to the present invention is performed at the end of the previous step, that is, at the end of the hydrothermal treatment step ii), or at the end of the ion exchange step iii), preferably at the end of the ion exchange step iii). including. Step iii) and step iv) of the preparation method can be advantageously reversed. Each of steps iii) and iv) may be optionally repeated.

In the heat treatment step iv), the solid is dried at a temperature of 20 to 150 ° C., preferably 60 to 100 ° C., preferably for 2 to 24 hours, followed by air, optionally in dry air, preferably 450 to. At a temperature of 700 ° C., preferably 500-600 ° C., for 2-20 hours, preferably 5-10 hours, more preferably 6-9 hours, the flow rate of any dry air is preferably 0. It comprises firing at least once at 5 to 1.5 L / h / g, more preferably 0.7 to 1.2 L / h / g of the solid to be treated. The temperature may be gradually increased prior to firing.
The catalyst obtained at the end of the heat treatment step iv) does not contain any organic species, especially the organic structuring agent R.

In particular, the catalyst obtained by the method comprising at least steps i), ii), iii) and iv) described above has improved NOx conversion properties.

Properties of Catalysts Prepared According to the Invention Catalysts include AFX-structured zeolites according to the International Zeolite Association (IZA) classification, exchanged by at least one transition metal. This structure is characterized by X-ray diffraction (XRD).

The X-ray diffraction (XRD) pattern is obtained by radiocrystallographic analysis with a diffractometer using a conventional powder method using _{copper K α1 radiation (λ = 1.5406 Å).} Based on the position of the diffraction peak represented by the angle 2θ, the lattice constant _{dhkl of the} sample is calculated by the Bragg reduction method. measurement error according to _{d hkl} Δ _{(d hkl)} is calculated by the Bragg Law in accordance with the absolute error assigned to the measurement of 2θ Δ (2θ). Absolute error Δ (2θ) equal to ± 0.02 ° is generally accepted. The _{relative intensity I rel} assigned to each value of _{d hkl} is measured according to the height of the corresponding diffraction peak. For example, DIFFRACT. By comparing the ICDD (International Center for Diffraction Data) database sheet with the diffraction pattern using software such as SUITE, it is also possible to identify the crystal phase present in the obtained substance.
Pure AFX-structured zeolite is used as standard.

Qualitative and quantitative analysis of the chemical species present in the resulting material is performed by X-ray fluorescence (XRF) spectroscopy. This is a technique for chemical analysis using the physical properties of substances and X-ray fluorescence. The spectrum of X-rays emitted by a substance is a characteristic of the composition of a sample, and by analyzing this spectrum, it is possible to estimate the element composition, that is, the mass concentration of the element.

The ignition loss (LOI) of the catalyst obtained after the calcination step (and before calcination) or after the calcination step of the method according to the invention is generally 4-15% by weight. The ignition loss of a sample referred to by the acronym LOI corresponds to the difference in mass of the sample before and after the heat treatment at 1000 ° C. for 2 hours. It is expressed as a percentage corresponding to the percentage of mass loss. Ignition loss generally corresponds to the loss of a solvent (such as water) present in the solid, but also corresponds to the removal of organic compounds contained in the inorganic solid component.

Use of Catalysts According to the Invention The present invention can also be directly prepared or prepared by the methods described above for the selective reduction of NOx with a reducing agent such as _{NH 3} or H _2. With respect to the use of the catalyst according to the present invention, the catalyst is advantageously coated (or "wash coat") on a honeycomb structure primarily for mobile applications, or especially on plate structures found in fixed applications. Formed by deposition in the form of.

Honeycomb structures are formed with parallel grooves (“flow-through grooves”) that are open at both ends, or are provided with porous filtration walls, in which adjacent parallel grooves alternate at both ends of the groove. The gas flow is forced to pass through the wall ("Wall Flow Monolith"). The honeycomb structure coated in this way constitutes a catalyst block. The structure may be composed of cordierite, silicon carbide (SiC), aluminum titanate (AlTi), α-alumina, mullite, or any other material having a porosity of 30-70%. The structure may be formed in a metal sheet in stainless steel (FeCrAl steel) containing chromium and aluminum.

The amount of the catalyst according to the present invention deposited on the structure is 50 to 180 g / L for the filtration structure and 80 to 200 g / L for the structure having the opening groove.

The actual washcoat contains the catalyst according to the present invention in combination with a binder such as serine, zirconium oxide, alumina, non-zeolite silica-alumina, titanium oxide, serine-zirconia mixed oxide, tungsten oxide, spinel and the like. do. The coating is advantageously applied to the structure by a deposition method known as a wash coating, which comprises a monolith in a solvent, preferably water, a powder catalyst according to the invention and optionally a binder, a metal oxide, and the like. Includes immersion in a suspension (or slurry) of stabilizer or other accelerator. This immersion step can be repeated until the desired amount of coating is obtained. In some cases, the slurry may be sprayed inside the monolith. Once the coating has settled, the monolith is fired at a temperature of 300-600 ° C. for 1-10 hours.

The structure may be coated with one or more coatings. The catalyst-containing coatings according to the invention advantageously have the ability to adsorb contaminants, especially NOx, reduce contaminants, especially NOx, or accelerate the oxidation of contaminants, especially ammonia. Combined, i.e. cover it or be covered by it.

Another option is that the catalyst is in the form of an extruded product. In this case, the obtained structure can contain up to 100% of the catalyst according to the present invention.

The catalyst-coated structure according to the present invention is an internal combustion engine that operates mainly in a dilute mixture mode, that is, with an excess amount of air relative to the stoichiometry of the combustion reaction, as in the case of a diesel engine, for example. Incorporated in the exhaust line of. Under these engine operating conditions, the exhaust gas specifically contains the following pollutants: soot, unburned hydrocarbons (HCs), carbon monoxide (CO), nitrogen oxides (NOx). An oxidation catalyst (whose function is to oxidize HCs and CO) and a filter for removing soot from the exhaust gas may be arranged upstream of the catalyst-coated structure according to the present invention. The function of the coated structure is to remove NOx, the working range of which is 100-900 ° C, preferably 200-500 ° C.

Advantages of the Invention AFX-structured zeolites and catalysts according to the invention based on at least one transition metal, in particular copper, have improved properties compared to prior art catalysts. In particular, by using the catalyst according to the present invention, while maintaining good selectivity to N 2 _O, over a lower light-off temperature and the entire operating temperature range for NOx conversion reaction (150 ℃ ~600 ℃) An improved NOx conversion rate can be obtained. It also has better resistance to hydrothermal aging and guarantees high performance even after such aging.

Example 1: Preparation of 1,6-bis (methylpiperidinium) hexanedihydroxyde (structuring agent R) 50 g of 1,6-dibromohexane (0.20 mol, 99%, Alfa Aesar), 50 g of N -Place in a 1 L round bottom flask containing methylpiperidine (0.51 mol, 99%, Alfa Aesar) and 200 mL of ethanol. The reaction medium is stirred under reflux for 5 hours. The mixture is then cooled to room temperature and filtered. The mixture is poured into 300 mL of cold diethyl ether, the precipitate formed is filtered and washed with 100 mL of diethyl ether. The resulting solid is recrystallized in an ethanol / ether mixture. The resulting solid is dried under vacuum for 12 hours. 71 g of white solid is obtained (ie, yield 80%).
The product has the expected ¹ H-NMR spectrum.
_{^{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 O (0.08 mol, 99%, Aldrich), 30 g of the prepared structuring agent 1,6-bis (methylpiperidinium) hexanedibromid (0.07 mol) and deionized. Place in a 250 mL Teflon® beaker containing 100 mL of water. The reaction medium is stirred for 12 hours in the absence of light. The mixture is then filtered. The resulting filtrate consists of an aqueous solution of 1,6-bis (methylpiperidinium) hexanedihydroxyde. This type of analysis is performed by proton NMR using formic acid as a reference material.

Example 2: Preparation of AFX-structured zeolite according to the present invention containing 3% Cu Preparation of AFX-structured zeolite 1645 g of FAU-structured zeolite (CBV780, SiO ₂ / Al ₂ O ₃ = 95.97, hexane, LOI = 9.30) %) Was mixed with an aqueous solution of 6424 g of 1,6-bis (methylpiperidinium) hexanedihydroxyde (18.36% by mass) prepared according to Example 1. 9114 g of deionized water is added to the previous mixture and the resulting preparation is continued to stir for 10 minutes. 164 g of sodium hydroxide (98% by weight, Aldrich) was incorporated into the synthetic mixture and stirred for 15 minutes. Next, an amorphous aluminum hydroxide gel (amorphous Al (OH) ₃ gel, Al ₂ O ₃ amount: 58.55 _{) corresponding to an Al 2} O ₃ (amorphous gel) / Al ₂ O _{3 (FAU) molar ratio of 6.49.} Incorporate 153.85 g (% by weight, Merck) and continue stirring the synthetic gel for 15 minutes. The molar composition of the precursor gel is as follows: 1 SiO ₂ : 0.05 Al ₂ O ₃ : 0.167 R: 0.093 Na ₂ O: 36.7 H ₂ O, ie SiO ₂ / Al _{The 2} O ₃ ratio is 20. The precursor gel is then homogenized and then transferred to a 25 L stainless steel reactor. The reactor is closed and then heated at 170 ° C. for 23 hours under self-sustaining pressure with stirring at 200 rpm using a system with four tilted paddles. The resulting solid crystal product is filtered off, washed with deionized water and then dried at 100 ° C. overnight. The LOI of the dry solid is 9.7%.

The solid is then introduced into the muffle furnace and the firing step is carried out: the firing cycle is a steady-state step where the temperature rises to 200 ° C. by 1.5 ° C./min, maintained at 200 ° C. for 2 hours, and 1 ° C./to 550 ° C. Includes a minute temperature rise followed by a steady-state step maintained at 550 ° C. for 8 hours, followed by a return to room temperature.
The calcined solid product was analyzed by X-ray diffraction and identified as consisting of an AFX-structured zeolite with a purity greater than 99%. _{The product has a SiO 2} / Al ₂ O ₃ molar ratio of 14.8, as determined by X-ray fluorescence.

The calcined AFX zeolite is _{brought into contact with a 3 mol NH 4} NO ₃ solution for 1 hour with stirring at 80 ° C. for _{NH 4} ^{+ ion exchange.} The ratio of the volume of the NH ₄ NO ₃ solution to the mass of the solid is 10. The resulting solid is filtered off, washed and the replacement procedure is repeated two more times under the same conditions. The final solid is separated, washed and dried at 100 ° C. for 12 hours. X-ray analysis shows that the product obtained is a pure AFX-structured zeolite in the form of ammonia.

Next, the ammonia form of AFX zeolite is treated under air flow at 550 ° C. for 8 hours with a temperature rise gradient of 1 ° C./min. Ignition loss (LOI) is 4% by weight. The product obtained is a protonated form of AFX zeolite.

Cu ion exchange Protonated calcined AFX zeolite is stirred at room temperature. Contact with a solution of [Cu (NH ₃ ) ₄ ] (NO ₃ ) _{2 for 1 day.} The final solid is separated, washed and dried at 100 ° C. for 12 hours.

The Cu-AFX exchanged solid obtained after contact with the solution of [Cu (NH ₃ ) ₄ ] (NO ₃ ) ₂ was calcined at 550 ° C. for 8 hours under air flow.
The calcined solid product was analyzed by X-ray diffraction and identified as an AFX-structured zeolite.
The product SiO ₂ / Al ₂ O ₃ molar ratio was 14.8, and the mass ratio of copper measured by fluorescent X-ray was 3%.
The obtained catalyst is referred to as CuAFX3.

Example 3: Preparation of AFX-structured zeolite according to the present invention containing 1% Cu Preparation of AFX-structured zeolite 1645 g of FAU-structured zeolite (CBV780, SiO ₂ / Al ₂ O ₃ = 95.97, Hexane, LOI = 9.30 %) Was mixed with an aqueous solution of 6424 g of 1,6-bis (methylpiperidinium) hexanedihydroxyde (18.36% by mass) prepared according to Example 1. 9114 g of deionized water is added to the previous mixture and the resulting preparation is continued to stir for 10 minutes. 164 g of sodium hydroxide (98% by weight, Aldrich) was incorporated into the synthetic mixture and stirred for 15 minutes. Next, an amorphous aluminum hydroxide gel (amorphous Al (OH) ₃ gel, Al ₂ O ₃ amount: 58.55 _{) corresponding to an Al 2} O ₃ (amorphous gel) / Al ₂ O _{3 (FAU) molar ratio of 6.49.} Incorporate 153.85 g (% by weight, Merck) and continue to stir the synthetic gel for 15 minutes. The molar composition of the precursor gel is as follows: 1 SiO ₂ : 0.05 Al ₂ O ₃ : 0.167 R: 0.093 Na ₂ O: 36.7 H ₂ O, ie SiO ₂ / Al _{The 2} O ₃ ratio is 20. The precursor gel is then homogenized and then transferred to a 25 L stainless steel reactor. The reactor is closed and then heated at 170 ° C. for 23 hours under self-sustaining pressure with stirring at 200 rpm using a system with four tilted paddles. The resulting crystal product is filtered off, washed with deionized water and then dried at 100 ° C. overnight. The LOI of the dry solid is 9.7%.

The solid is then introduced into the muffle furnace and the firing step is carried out: the firing cycle is a steady-state step where the temperature rises to 200 ° C. by 1.5 ° C./min, maintained at 200 ° C. for 2 hours, and 1 ° C./to 550 ° C. Includes a minute temperature rise followed by a steady-state step maintained at 550 ° C. for 8 hours, followed by a return to room temperature.
The calcined solid product was analyzed by X-ray diffraction and identified as consisting of an AFX-structured zeolite with a purity greater than 99%. _{The product has a SiO 2} / Al ₂ O ₃ molar ratio of 14.8, as determined by X-ray fluorescence.

The calcined AFX zeolite is _{brought into contact with a 3 mol NH 4} NO ₃ solution for 1 hour with stirring at 80 ° C. for _{NH 4} ^{+ ion exchange.} The ratio of the volume of the NH ₄ NO ₃ solution to the mass of the solid is 10. The resulting solid is filtered off, washed and the replacement procedure is repeated two more times under the same conditions. The final solid is separated, washed and dried at 100 ° C. for 12 hours. X-ray analysis shows that the product obtained is a pure AFX-structured zeolite in the form of ammonia.

AMX zeolite in ammonia form is treated under air flow at 550 ° C. for 8 hours at a temperature rise gradient of 1 ° C./min. Ignition loss (LOI) is 4% by weight. The product obtained is a protonated form of AFX zeolite.

Cu Ion Exchange Protonated calcined AFX zeolite 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 at 100 ° C. for 12 hours.

The Cu-AFX exchanged solid obtained after contact with the solution of [Cu (NH ₃ ) ₄ ] (NO ₃ ) ₂ was calcined at 550 ° C. for 8 hours under air flow.
The calcined solid product was analyzed by X-ray diffraction and identified as an AFX-structured zeolite.
The product SiO ₂ / Al ₂ O ₃ molar ratio was 14.8, and the mass ratio of copper measured by fluorescent X-ray was 1%.
The obtained catalyst is referred to as CuAFX1.

Example 4: In this example, Cu exchange SSZ-16 zeolite is synthesized according to the prior art. In this example, copper is introduced by ion exchange.
Preparation of SSZ-16 Zeolite Dissolve 17.32 g of sodium hydroxide in 582.30 g of deionized water with stirring (300 rpm) at room temperature. Add 197.10 g of sodium silicate to this solution and homogenize the whole with stirring (300 rpm at room temperature). Then, 9.95 g of NaY zeolite CBV100 is added with stirring (300 rpm), and this is continued until the zeolite is dissolved. 43.67 g of the structuring agent DABCO-C4 is dissolved in the solution thus obtained, and 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
The reaction mixture obtained in the mixing step is continuously stirred at room temperature for 24 hours.
The obtained gel is left in an autoclave at a temperature of 150 ° C. for 6 days with stirring (200 rpm). The obtained crystals are separated and washed with deionized water until the pH of the washing water becomes less than 8. The washed crystalline solid is dried at 100 ° C. for 12 hours.
XRD analysis shows that the resulting product is a pure crude SSZ-16 zeolite with an AFX structure (ICDD sheet, PDF 04-03-1370).
The crude synthetic SSZ-16 zeolites, dry _{N 2} under a stream for 8 hours at 550 ° C., and then a stream of dry air and calcined for 8 hours at 550 ° C.. Ignition loss (LOI) is 18% by weight.

The calcined SSZ-16 zeolite is _{brought into contact with a 3 mol NH 4} NO ₃ solution for 5 hours with stirring at room temperature for _{NH 4} ^{+ ion exchange.} The ratio of the volume of the NH ₄ NO ₃ solution to the mass of the solid is 10. The resulting solid is filtered off, washed and the replacement procedure is repeated under the same conditions. The final solid is separated, washed and dried at 100 ° C. for 12 hours.

Ammonia form SSZ-16 zeolite (NH ₄ -SSZ-16) is treated under dry air flow at 550 ° C. for 8 hours at a temperature rise gradient of 1 ° C./min. Ignition loss (LOI) is 4% by weight. The product obtained is a protonated form of SSZ-16 zeolite (H-SSZ-16).

Cu Ion Exchange on H-SSZ-16 The H-SSZ-16 zeolite is contacted 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, dried and calcined under dry air at 550 ° C. for 8 hours. XRD analysis shows that the product obtained is a pure AFX structure SSZ-16 zeolite (ICDD sheet, PDF 04-03-1370).
In the chemical analysis by fluorescent X-ray, _{the molar ratio of SiO 2} / Al ₂ O ₃ was 13, and the mass ratio of Cu was 3%.
The obtained catalyst is designated as CuSSZ16.

Example 5: Hydrothermal aging step 200 mg of each of the powdered samples synthesized according to Example 2 (CuAFX3), Example 3 (CuAFX1) and Example 4 (CuSSZ16) is placed in a quartz reactor. A mixture having the following molar composition: 10% H ₂ O, 20% O ₂ and the balance N ₂ are passed through the sample at a flow rate of 150 L / h. Samples are subjected to these conditions at a temperature of 800 ° C. for 4 hours. Then it cooled them to room temperature under a stream of N _2.

Example 6
A sample synthesized according to Example 2 and aged under the conditions of Example 5 is designated as CuAFX3 aged.
A sample synthesized according to Example 3 and aged under the conditions of Example 5 is designated as CuAFX1 aged.
A sample synthesized according to Example 4 and aged under the conditions of Example 5 is designated CuSSZ16aged.

Example 7: NOx conversion under standard SCR conditions: Comparison of the catalyst according to the present invention with the prior art For catalysts synthesized according to Example 2 (CuAFX3), Example 3 (CuAFX1) and Example 4 (CuSSZ16), standard SCR conditions. Underneath, catalytic tests for the reduction of nitrogen oxides (NOx) by _{ammonia (NH 3} ) in the presence of oxygen (O _{2) are performed at various operating temperatures.}
For testing each sample, 200 mg of catalyst in powder form is placed in a quartz reactor. A mixture of exhaust gases from a diesel engine is supplied to the reactor with a typical loading of 145 L / h.
This loading has the following molar composition: 400ppm NO, 400ppm NH ₃ , 8.5% O ₂ , 9% CO ₂ , 10% H ₂ O, balance N ₂ .
An FTIR analyzer was used to measure the concentrations of NO, NO ₂ , NH ₃ , N ₂ O, CO, CO ₂ , H ₂ O, and O _{2 at the reactor outlet.} The calculated NOx conversion rate is as follows:
Conversion rate = (NOx inlet-NOx exit) / NOx inlet

The results of the NOx conversion rate are shown in FIG. 3, and the curves shown by squares, circles, and triangles are for tests performed using catalysts synthesized according to Example 2 (CuAFX3), Example 3 (CuAFX1), and Example 4 (CuSSZ16), respectively. handle. It seems that the catalyst according to the present invention can be used to convert NOx.
The catalyst CuAFX1 synthesized according to the present invention is particularly effective at high temperatures, has a NOx conversion rate of 350 ° C to 100%, and its effectiveness remains above 95% up to 550 ° C. The catalyst CuAFX3 synthesized according to the present invention gives much better results than the catalyst synthesized according to the prior art in terms of NOx conversion over the entire temperature range tested. A maximum conversion of 100% is achieved for the catalyst CuAFX3 between 270-410 ° C., while the catalyst CuSSZ16 synthesized according to the prior art achieves only 89% conversion between 340-400 ° C.

The light-off temperatures of catalysts containing 3% copper under standard SCR conditions are shown below:

T50 corresponds to the temperature at which 50% of NOx in the gas mixture is converted by the catalyst. T80 corresponds to the temperature at which 80% of NOx in the gas mixture is converted by the catalyst. T90 corresponds to the temperature at which 90% of NOx in the gas mixture is converted by the catalyst. T100 corresponds to the temperature at which 100% of NOx in the gas mixture is converted by the catalyst.
The catalyst CuAFX3 synthesized according to the present invention provides much better results than the catalyst CuSSZ16 synthesized according to the prior art in terms of light-off temperature and NOx conversion over the entire temperature range tested under standard SCR conditions. In fact, at the same conversion rate (50% or 80%), the light-off temperature obtained with the catalyst CuAFX3 according to the present invention is lower than the light-off temperature obtained with the catalyst CuSSZ16.

Example 8: NOx conversion under high-speed SCR conditions For the catalyst synthesized in Example 4 of the present invention and the sample CuSSZ16 (Example 5) synthesized according to the prior art, under high-speed SCR conditions in the presence of _{oxygen (O 2).} Catalytic tests for the reduction of nitrogen oxides (NOx) with ammonia (NH _{3) are performed at various operating temperatures.}
200 mg of the catalyst in powder form is placed in a quartz reactor. A mixture of exhaust gases from a diesel engine is supplied to the reactor with a typical loading of 218 L / h. This loading under high speed SCR conditions has the following molar composition: 200 ppm NO, 200 ppm NO ₂ , 400 ppm NH ₃ , 8.5% O ₂ , 9% CO ₂ , 10% H ₂ O, balance N ₂ .
An FTIR analyzer was used to measure the concentrations of NO, NO ₂ , NH ₃ , N ₂ O, CO, CO ₂ , H ₂ O, and O _{2 at the reactor outlet.} The calculated NOx conversion rate is as follows:
Conversion rate = (NOx inlet-NOx exit) / NOx inlet

The results of the NOx conversion rate are shown in FIG. 4, and the curves shown by squares, circles, and triangles are for tests performed using catalysts synthesized according to Example 2 (CuAFX3), Example 3 (CuAFX1), and Example 4 (CuSSZ16), respectively. handle.

The catalyst light-off temperature under high speed SCR conditions is shown below:

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

The catalysts CuAFX1 and CuAFX3 synthesized according to the present invention give better results than the catalyst CuSSZ16 synthesized according to the prior art in terms of light-off temperature and NOx conversion over the entire temperature range tested under high speed SCR conditions. In fact, at the same conversion rate (50%, 80%, 90% or 100%), the light-off temperature obtained with the catalysts CuAFX1 and CuAFX3 according to the present invention is lower than the light-off temperature obtained with the catalyst CuSSZ16.
Furthermore, the release of nitrous oxide _(N 2 O), in the case of the catalyst CuAFX1 and CuAFX3 according to the present invention, (<15 ppm at 150 to 550 ° C.) remained low in that over the entire temperature range tested.

Example 9: NOx conversion under standard and fast SCR conditions after hydrothermal aging Reduction of nitrogen oxides (NOx) by _{ammonia (NH 3} ) in the presence of _{oxygen (O 2) under standard and fast SCR conditions} The catalyst test for this is performed at various operating temperatures for the catalysts shown as CuAFX3aged and CuSSZ16aged, which were synthesized according to Examples 2 and 4 and then aged according to the method described in Example 5.
200 mg of the catalyst in powder form is placed in a quartz reactor. A mixture of exhaust gases is fed to the reactor with a typical loading of 145 L / h. This loading was carried out under standard SCR conditions with the following molar composition: 400 ppm NO, 400 ppm NH ₃ , 8.5% O ₂ , 9% CO ₂ , 10% H ₂ O, balance N ₂ and under fast SCR conditions: Molar composition: 200ppm NO, 200ppm NO ₂ , 400ppm NH ₃ , 8.5% O ₂ , 9% CO ₂ , 10% O, with balance N ₂ .
An FTIR analyzer was used to measure the concentrations of NO, NO ₂ , NH ₃ , N ₂ O, CO, CO ₂ , H ₂ O, and O _{2 at the reactor outlet.} The calculated NOx conversion rate is as follows:
Conversion rate = (NOx inlet-NOx exit) / NOx inlet

FIG. 5 shows the NOx conversion rate by the catalysts CuAFX3aged and CuSSZ16aged as a function of temperature under standard SCR conditions.

The catalyst light-off temperatures under standard SCR conditions are shown below:

The light-off temperature of the catalyst under high-speed SCR conditions is shown below.

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

The catalyst CuAFX3 synthesized according to the present invention is much better than the catalyst CuSSZ16 synthesized according to the prior art in terms of light-off temperature and NOx conversion over the entire temperature range tested under standard SCR conditions after hydrothermal aging. Brings good results. In fact, at the same conversion rate (50%), the light-off temperature obtained with the catalyst CuAFX3 according to the present invention is lower than the light-off temperature obtained with the catalyst CuSSZ16. A conversion rate of 100% is achieved between 275 and 330 ° C. for the catalyst CuAFX3, while only 66% conversion rate is achieved at 330 ° C. for the catalyst CuSSZ16.
The results under high speed SCR conditions are also good for the catalyst CuAFX3aged synthesized according to the present invention, with a maximum conversion of 100%, achieved between 225-360 ° C., while the catalyst CuSSZ16aged is 305-. Only up to 78% is achieved between 360 ° C.
Release of nitrous oxide _(N 2 O) is equivalent for the two catalysts tested (<15 ppm at 150 to 550 ° C.).

Claims (32)

A method for preparing a catalyst based on an AFX-structured zeolite and at least one transition metal, which comprises at least the following steps:
_{i) In an aqueous medium, a FAU-structured zeolite having a SiO 2 (FAU)} / Al ₂ O _{3 (FAU)} molar ratio of 6.0 to 200 (including the limit value) and an organic nitrogen compound R (R is 1). , 5-Bis (Methylpiperidinium) Pentane Dihydroxydo, 1,6-bis (Methylpiperidinium) Hexanedihydroxydo or 1,7-Bis (Methylpiperidinium) Heptanedihydroxydo), At least one alkali and / or alkaline earth metal with valence n At least one source of M (n is an integer greater than or equal to 1 and M is lithium, potassium, sodium, magnesium and calcium and at least one of these metals. (Choose from a mixture of the two) and is mixed until a homogeneous precursor gel is obtained.
The reaction mixture has the following molar composition:
(SiO _{2 (FAU)} ) / (Al ₂ O _{3 (FAU)} ) is 6.0 to 200, preferably 6.0 to 100,
H ₂ O / (SiO _{2 (FAU)} ) is 1.00 to 100, preferably 5 to 60,
R / (SiO _{2 (FAU)} ) is 0.01 to 0.60, preferably 0.05 to 0.50.
M _{2 / n} O / (SiO _{2 (FAU)} ) is 0.005 to 0.45, preferably 0.05 to 0.25.
However, including the limit value
_{Here, SiO 2 (FAU)} indicates the amount of SiO ₂ provided by the FAU _zeolites, Al _{2 O 3 (FAU)} indicates the amount of _Al 2 _{O 3} which is provided by the FAU zeolite;
ii) Hydrothermal treatment of the precursor gel obtained at the end of step i) for 12 hours to 15 days at a temperature of 120 ° C to 220 ° C to obtain a solid crystalline phase, i.e. "solid";
iii) The solid obtained at the end of the previous step is stirred at room temperature for 1 hour to 2 days to release at least one species capable of releasing transition metals, especially copper, in a solution in reactive form. At least one ion exchange, including contacting with the containing solution;
iv) Heat treatment by drying the solid obtained at the end of the previous step at a temperature of 20 to 150 ° C., and then firing at least once at a temperature of 400 to 700 ° C. under air flow. The method according to claim 1, wherein steps iii) and iv) are reversed and arbitrarily repeated. The reaction mixture of step i) _{comprises at least one additional source of XO 2} oxide, where X is one or more tetravalent elements selected from the group formed by the following elements: silicon, germanium, titanium: The XO ₂ / SiO _{2 (FAU)} molar ratio is 0.001 to 1, preferably 0.001 to 0.9, more preferably 0.001 to 0.01, but includes a limit value. The method according to claim 1 or 2, wherein the SiO _{2 (FAU)} content in the ratio is the content provided by the FAU-structured zeolite. The method of claim 3, wherein the reaction mixture of step i) has the following molar composition:
(XO ₂ + SiO _{2 (FAU)} ) / Al ₂ O _{3 (FAU)} is 6.0 to 200, preferably 6.0 to 100,
H ₂ O / (XO ₂ + SiO _{2 (FAU)} ) is 1 to 100, preferably 5 to 60.
R / (XO ₂ + SiO _{2 (FAU)} ) is 0.01 to 0.6, preferably 0.05 to 0.5,
M _{2 / n} O / (XO ₂ + SiO _{2 (FAU)} ) is 0.005 to 0.45, preferably 0.05 to 0.25, but includes a limit value. The method according to any one of claims 3 to 4, wherein X is silicon. The reaction mixture of step i) _{comprises at least one additional source of Y 2} O ₃ oxide, where Y is one or more trivalents selected from the group formed by the following elements: aluminum, boron, gallium. It is an element and has a Y ₂ O ₃ / Al ₂ O _{3 (FAU)} molar ratio of 0.001 to 10, preferably 0.001 to 8, but includes a limit value and is Al ₂ O _{3 (in the above ratio).} The method according to one of the preceding claims, wherein the _{FAU) content is the content provided by the FAU-structured zeolite.} The method of claim 6, wherein the reaction mixture of step i) has the following molar composition:
SiO _{2 (FAU)} / (Al ₂ O _{3 (FAU)} + Y ₂ O ₃ ) is 6.0 to 200, preferably 6.0 to 100,
H ₂ O / SiO _{2 (FAU)} is 1-100, preferably 5-60,
R / SiO _{2 (FAU)} is 0.01 to 0.6, preferably 0.05 to 0.5,
M _{2 / n} O / SiO _{2 (FAU)} is 0.005 to 0.45, preferably 0.05 to 0.25.
However, including the limit value
SiO _{2 (FAU)} is the amount of _{SiO 2} provided by the FAU zeolite _{, and Al 2} O _{3 (FAU)} is the amount of _{Al 2} O ₃ provided by the FAU zeolite. The method according to any one of claims 6 to 7, wherein Y is aluminum. The reaction mixture of step i)
Includes _{at least one additional source of -XO 2} oxide-and at least one additional source of Y ₂ O ₃ oxide.
The FAU zeolite is 5 to 95% by mass, preferably 50, based on the total amount of the trivalent and tetravalent elements SiO _{2 (FAU)} , XO ₂ , Al ₂ O _{3 (FAU)} and Y ₂ O _{3 in the reaction mixture.} The method according to one of the preceding claims, wherein the reaction mixture comprises ~ 95% by weight, very preferably 60-90% by weight, even more preferably 65-85% by weight, and the reaction mixture has the following molar composition:
(XO ₂ + SiO _{2 (FAU)} ) / (Al ₂ O _{3 (FAU)} + Y ₂ O ₃ ) is 6.0 to 200, preferably 6.0 to 100,
H ₂ O / (XO ₂ + SiO _{2 (FAU)} ) is 1 to 100, preferably 5 to 60.
R / (XO ₂ + SiO _{2 (FAU)} ) is 0.01 to 0.6, preferably 0.05 to 0.5,
M _{2 / n} O / (XO ₂ + SiO _{2 (FAU)} ) is 0.005 to 0.45, preferably 0.05 to 0.25, but includes a limit value. The molar ratio of the total amount of the precursor gel obtained at the end of step i) as the oxide of the tetravalent element to the total amount of the oxide of the trivalent element is 6.0 to 100 (including the limit value). ), The method according to one of the preceding claims. The method according to one of the preceding claims, wherein the _{FAU structure zeolite has a SiO 2} / Al ₂ O ₃ molar ratio of 6.0 to 100 (including a limit value). The seed crystal of the AFX-structured zeolite is preferably 0.01 to 10% by mass based on the total mass of the anhydrous tetravalent and trivalent element present in the reaction mixture of step i). The method of one of the preceding claims, wherein the seed crystal is added in an amount of, and the seed crystal is not considered in the total mass of the source of tetravalent and trivalent elements. The method according to one of the preceding claims, wherein step i) comprises aging the reaction mixture at a temperature of 20-100 ° C. for 30 minutes-48 hours with or without stirring. The hydrothermal treatment of step ii) is carried out at a temperature of 120 ° C. to 220 ° C., preferably 150 ° C. to 195 ° C. for 12 hours to 12 days, preferably 12 hours to 10 days under self-sustaining pressure. 13. The method according to any one of 13. At least one, preferably only one, in which the ion exchange step iii) can contact the solid with a solution containing only one species capable of releasing the transition metal, or each can release the transition metal. The method of any one of claims 1-14, wherein the transition metals of the various solutions are preferably different from each other, carried out by the continuous contact of the solid with various solutions containing the seeds. The group in which the at least one transition metal released into the exchange solution of step iii) is formed from the following elements: Ti, V, Mn, Mo, Fe, Co, Cu, Cr, Zn, Nb, Ce, Selected from the group formed of Zr, Rh, Pd, Pt, Au, W, Ag, preferably the following elements: Fe, Cu, Nb, Ce or Mn, more preferably Fe or Cu. Even more preferably, the method according to claim 15, wherein the transition metal is Cu. The content of the transition metal introduced by the ion exchange step iii) is 0.5 to 6% by mass, preferably 0.5 to 5% by mass, and more preferably 1 to 4 with respect to the total mass of the final anhydrous catalyst. The method according to one of the preceding claims, which is mass%. The heat treatment step iv) dries the solid at a temperature of 20 to 150 ° C., preferably 60 to 100 ° C. for 2 to 24 hours, followed by air, optionally in dry air, 450 to 700 ° C., preferably 500 to. At a temperature of 600 ° C. for 2-20 hours, preferably 5-10 hours, more preferably 6-9 hours, the flow rate of any dry air is preferably 0.5-1.5 L / h / of the solid being treated. The method according to one of the preceding claims, comprising firing at least once at 0.7-1.2 L / h / g of g, more preferably the solid to be treated. A catalyst based on AFX zeolite and at least one transition metal, obtained by the method according to any one of claims 1-18. Group in which the transition metal is formed from the following elements: Ti, V, Mn, Mo, Fe, Co, Cu, Cr, Zn, Nb, Ce, Zr, Rh, Pd, Pt, Au, W, Ag, preferably. Is selected from the group formed from the following elements: Fe, Cu, Nb, Ce or Mn, more preferably from the group formed from Fe or Cu, and even more preferably the transition metal is Cu. 19. The catalyst according to 19. 19. The total content of the transition metal is 0.5 to 6% by mass, preferably 0.5 to 5% by mass, more preferably 1 to 4% by mass, based on the total mass of the final anhydrous catalyst. The catalyst according to any one of 20 to 20. 28. catalyst. Copper is included in combination with at least one other transition metal selected from the group formed from Fe, Nb, Ce, Mn and the copper content in the catalyst is relative to the total mass of the final anhydrous catalyst. It is 0.05 to 2% by mass, preferably 0.5 to 2% by mass, and the content of the at least one other transition metal is 1 to 4% by mass with respect to the total mass of the final anhydrous catalyst. 21. The catalyst according to claim 21. Iron is contained in combination with other metals selected from the group formed from Cu, Nb, Ce, Mn, and the iron content is 0.05-2% by mass, based on the total mass of the final anhydrous catalyst. The catalyst according to claim 21, wherein the content of the other transition metal is preferably 0.5 to 2% by mass, and the content of the other transition metal is 1 to 4% by mass based on the total mass of the final anhydrous catalyst. The catalyst according to any one of claims 19 to 24, or the method according to any one of claims 1 to 18, for the selective reduction of NOx with a reducing agent such as NH ₃ or H _2. Use of the resulting catalyst. 25. The use of claim 25, wherein the catalyst is formed by depositing on a honeycomb structure or plate structure in the form of a coating. Claim that the honeycomb structure is formed by parallel grooves that are open at both ends or comprises a porous filtration wall, where adjacent parallel grooves are alternately blocked at both ends of the groove. Use according to 26. 27. The use according to claim 27, wherein the amount of catalyst deposited on the structure is 50-180 g / L for a filtered structure and 80-200 g / L for a structure with an opening groove. Combined with binders such as serine, zirconium oxide, alumina, non-zeolite silica-alumina, titanium oxide, serine-zirconia mixed oxides, tungsten oxide and / or spinel because the catalyst is formed by deposition in the form of a coating. The use according to any one of claims 25 to 28. Any one of claims 26-29, wherein said coating is combined with other coatings capable of adsorbing contaminants, especially NOx, reducing contaminants, especially NOx, or promoting oxidation of contaminants. Use as described in. 25. The use according to claim 25, wherein the catalyst is in the form of an extrude containing up to 100% of the catalyst. The use according to any one of claims 25 to 31, wherein the structure coated by the catalyst or obtained by extrusion of the catalyst is incorporated in an exhaust line of an internal combustion engine.

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