WO2020025846A1

WO2020025846A1 - Method for synthesising mww material in its nanocrystalline form and its use in catalytic applications

Info

Publication number: WO2020025846A1
Application number: PCT/ES2019/070537
Authority: WO
Inventors: Eva María GALLEGO SÁNCHEZ; Cecilia Gertrudis PARIS CARRIZO; María Cristina MARTÍNEZ SÁNCHEZ; Manuel MOLINER MARÍN; Avelino Corma Canos
Original assignee: Universitat Politècnica De València; Consejo Superior De Investigaciones Científicas (Csic)
Priority date: 2018-08-01
Filing date: 2019-07-29
Publication date: 2020-02-06
Also published as: ES2739646B2; ES2739646A1

Abstract

The invention relates to a method for synthesising a material with an MWW zeolite structure in its nanocrystalline form, which comprises the following steps: i) preparing a mixture comprising a water source, at least one source of a tetravalent element Y, at least one source of a trivalent element X, at least one source of an alkaline cation or alkaline earth metal cation (A), and at least two organic molecules (ADE01 and ADE02), wherein ADE01 is a monocyclic quaternary ammonium in which one of the substituents is an alkyl chain of 3-6 carbon atoms, and ADE02 is selected from any amine or ammonium able to direct the formation of MWW; ii) crystallising the mixture obtained in step i) in a reactor; and iii) recovering the crystalline material obtained in step ii).

Description

SYNTHESIS PROCEDURE OF THE MWW MATERIAL IN ITS FORM

NANOCRISTALINE AND ITS USE IN CATALYTIC APPLICATIONS

Technical Field

The present invention relates to a new method of synthesis of the zeolite with MWW crystalline structure in its nanocrystalline form, as well as the use as a catalyst of the zeolitic material synthesized according to the present synthesis procedure.

Background

Zeolites are microporous materials with crystalline structures formed by tetrahedra T0 ₄ (T = Si, Al, P, Ti, Ge, Sn ...) interconnected by oxygen atoms, which are arranged forming pores and cavities of molecular dimensions (3- 15 Á) uniforms in size and shape. The International Association of Zeolites (IZA) has accepted more than 230 zeolites (http://www.iza-online.org) with different topology, zeolites that can be classified according to the size of their pores, whose openings or windows are delimited by a number T of atoms. Thus, small pore zeolites have windows delimited by 8 T atoms, medium pore zeolites have windows delimited by 10 T atoms, medium pore zeolites have windows delimited by 12 T atoms, and extra-large pore zeolites they have windows delimited by more than 12 T atoms. In general, it can be indicated that zeolitic structures, depending on their chemical composition (eg aluminosilicates), are traditionally anionic and, therefore, can be compensated by cations, such as cations alkaline and / or alkaline earth (eg Na, K, Ca, Mg, among others), ammonium cations, protons, and also any cation of a metallic nature, such as (Cu, Pd, Pt, Rh, Au, among others).

Thanks to this great variety of structures and the possibility of modifying the chemical composition of most zeolites, these materials have numerous applications in adsorption processes, ion exchange and as heterogeneous catalysts in the refining, petrochemical and environmental fields (Nature 2002 , 417, 813; Coord. Chem. Rev. 2011, 255, 1558).

In its application as heterogeneous catalysts, the presence of pores and cavities of molecular dimensions gives zeolites the so-called shape selectivity, exerted by their structure to reactants, transition states or products involved in the reaction However, the reduced dimensions of these channel systems can also cause problems of diffusion of more bulky molecules, which will have direct consequences on their activity, selectivity and deactivation rate, and will lead to underutilization of the zeolitic material. For these reasons it may be convenient to decrease the length of the pores of the zeolite and, therefore, the length of the diffusion paths. There are different proposals to reduce the length of the channels, such as the generation of intracrystalline mesoporosity by direct synthesis by means of hard templating methods or by post-synthesis demetalization treatments (Chem. Soc. Rev. 2008, 37, 2530; Micropor, Mesopor, Mater. 2003, 65, 59). Another alternative to reduce the length of the pores is to reduce the crystal size of the zeolites, from microscopic dimensions to nanoscopic dimensions, in particular, below 100 nm (Chem. Soc. Rev. 2015, 44, 1201-1233) .

The MWW zeolitic structure is composed of two independent pore systems, one of which is formed by large cavities of -0.7x1.8 nm connected by openings delimited by rings of 10 T atoms, and the other is defined by a circular channel of 10 T atoms. The external surface of the MWW structure exposes half of the large cavities, generating a kind of superficial “cups”. Different research groups have described various synthesis methodologies in order to control the crystal size of zeolites with MWW structure in their nanometric scale (less than 100 nm), at least in some dimension of crystals with MWW structure. For this, and in general, the use of bulky organic compounds is required, such as cations of a surfactant nature (Nature, 1998, 396, 353; Chem. Sci., 2015, 6, 6320; Angew. Chem. Int. Ed ., 2015, 54, 13724) or cationic polymers (Cata !. Commun., 2014, 43,218). These bulky ADEs described for these synthesis processes usually have long aliphatic chains and / or require the use of numerous stages of synthesis, which may make the preparation of the MWW structure more expensive.

It is also important to note that the methods that present the use of organic molecules of a surfactant nature with long aliphatic chains (> 12 carbons) direct the crystallization of the MWW material with sizes smaller than 10 nm along the crystallographic axis [001] , but, on the contrary, it does not allow reducing the dimensions along the crystallographic axes [100] and [010] below 300 nm (Nature, 1998, 396, 353; Chem. Sci., 2015, 6, 6320; Angew. Chem. Int. Ed., 2015, 54, 13724). The reduction of the MWW crystal size below 100 nm in the [100] and [010] axes would be very important, since it would allow a better diffusion along the circular channels of 10 T atoms, allowing in turn better accessibility to the large cavities present in the MWW structure.

The preparation of the MWW zeolite with heterogeneous crystal sizes, with ranges between 10-900 nm or 50-300 nm, has recently been described using MWW crystals as sowing in the synthesis gel (CN 104528757; Shiyou Huagong, 2012, 41, 19-21, respectively).

Despite the background found in the literature and described in the previous paragraphs, there is a clear need for the chemical industry to improve the synthesis of the MWW zeolite in its nanocrystalline form and, in particular, to synthesize it with morphologies in which reduce the crystal size in the crystallographic directions [100] and [010] using simple organic molecules, for later application as a catalyst and / or adsorbent in various catalytic processes, and more particularly, for use in alkylation processes of aromatics with light olefins, selective catalytic reduction (RCS) of NOx, or as a passive adsorbent of NOx at low temperatures.

Description of the Invention

The present invention relates to a new method of synthesis of a crystalline material that presents the MWW zeolitic structure in its nanocrystalline form using simple organic molecules, where the size of the crystals of said zeolitic material along the crystallographic directions [100] and [010] is on average in the range of 10 to 100 nm, and along the crystallographic direction [001] is on average in the range of 2 to 50 nm. The axes [100] and [010] define the circular channels of 10 T atoms present in the MWW structure, which allow improving accessibility to the large cavities present in the MWW structure. The present invention also relates to the subsequent use of said synthesized material as a catalyst and / or adsorbent in various catalytic processes, preferably as a catalyst in aromatic alkylation processes with light olefins, as a catalyst for the selective catalytic reduction (RCS) of NOx, or as a passive NOx adsorbent at low temperatures. This new method of synthesis of a zeolitic material with the MWW structure in its nanocrystalline form can comprise at least the following steps:

i) Preparation of a mixture comprising at least one source of water, at least one source of a tetravalent element Y, at least one source of a trivalent element X, at least one source of an alkaline or alkaline earth cation (A), and at least two organic molecules (ADE01 and ADE02), where ADE01 is selected from a monocyclic quaternary ammonium where at least one of the substituents is a linear alkyl chain consisting of 3-6 carbon atoms, and ADE02 is selected from any amine or ammonium capable of directing the synthesis to crystallization of a zeolite with MWW structure. The molar composition of the mixture is:

/ X ₂ 0 ₃ : Y0 ₂ : m ADE01: n ADE02: a A. and H ₂ 0 where

/ is in the range of 0 to 0.5, preferably between 0.003 to 0.1; and more preferably between 0.01 to 0.075.

m is in the range of 0.01 to 1, preferably between 0.01 to 0.5; and more preferably between 0.05 to 0.2.

n is in the range of 0.01 to 2, preferably between 0.05 to 1; and more preferably between 0.1 to 0.6.

a is in the range of 0 to 2, preferably 0 to 1; and more preferably between 0 to 0.8.

and is in the range of 2 to 200, preferably between 5 to 150, and more preferably between 7 to 75.

ii) Crystallization of the mixture obtained in i) in a reactor

iii) Recovery of the crystalline material obtained in ii)

According to a particular embodiment, the source of the tetravalent element Y may be selected from silicon, tin, titanium, zirconium, germanium, and combinations thereof. Preferably, the source of element Y is a source of silicon that may be selected from silicon oxide, silicon halide, colloidal silica, smoking silica, tetraalkyl ortho silicate, silicate, silicic acid, a previously synthesized crystalline material, a previously synthesized material amorphous and combinations thereof.

According to a particular embodiment, the source of Si may be selected from a previously synthesized crystalline material, a previously synthesized amorphous material and combinations thereof, and which may also contain other heteroatoms in their structure. Some examples could be zeolites type faujasita (FAU), type L (LTL) and mesoporous materials ordered amorphous, such as MCM-41.

According to a preferred embodiment, the trivalent element X may be selected from aluminum, boron, iron, indium, gallium and combinations thereof, preferably between Al, B and combinations thereof and, more preferably Al.

According to a particular embodiment, the trivalent element X is aluminum. The aluminum source may be selected from at least any aluminum salt (eg aluminum nitrate), or any hydrated aluminum oxide.

According to a particular embodiment, the zeolite with MWW structure can be found in its aluminosilicate, metalaluminosilicate, borosilicate, aluminoborosilicate or purely siliceous form, being preferably selected from the zeolite MCM-22, ERB-1, SSZ-25, ITQ- 1, or any of its disorganized and / or pilareadas variants, as well as the MCM-56, MCM-49, ITQ-30 or SSZ-70 or any of its delaminated variants, such as ITQ-2, DS-ITQ-2 and / or MIT-1.

According to a particular embodiment, the zeolite with MWW structure is in its aluminosilicate form, and it is the MCM-22 zeolite.

According to a particular embodiment of the present invention, the ADE01 may be selected from a quaternary ammonium monocyclic structure RiR2CicloN ^+, where the cycle group may be formed from 4-8 carbon atoms, and Ri and _R2 groups can be strings linear alkyl between 1-4 and 3-6 carbon atoms, respectively.

In the present invention, the term "Cycle" refers to a linear alkyl chain of between 4-8 carbon atoms, optionally substituted by an alkyl of 1 to 3 carbon atoms, preferably a methyl, whose terminal carbons are attached to the N of the corresponding quaternary ammonium, so that said linear alkyl chain next to the N atom forms a heterocycle.

According to a particular embodiment of the present invention, ADE01 may be selected from alkyl-pyrrolidiniums, alkyl-piperidiniums, alkyl-hexamethylene ammoniums, alkyl-heptamethylene ammoniums and combinations thereof, preferably may be an alkyl hexamethylene ammonium and more preferably it is / V-butyl-A / - methyl hexamethylene ammonium.

According to a particular embodiment of the present invention, ADE02 may be selected from any amine or ammonium that directs the synthesis towards the crystallization of zeolite with MWW structure, and combinations thereof.

According to a particular embodiment of the present invention, ADE02 may be selected from primary, secondary or tertiary amines, diamines or polyamines, or quaternary ammoniums, diamonds or polyammoniums, and combinations thereof.

According to a particular embodiment of the present invention, ADE02 may be selected from pyrrolidines, piperidines, hexamethyleneimines, heptamethyleneimines, pyrrolidiniums, piperidiniums, hexamethylene ammoniums, heptamethylene ammonia, their alkylated derivatives, and combinations thereof. Preferably ADE02 may be pyrrolidine, piperidine, hexamethyleneimine or combinations thereof and more preferably it is hexamethyleneimine.

According to the present invention, the crystallization step described in ii) can preferably be carried out in an autoclave, under conditions that can be static or dynamic at a temperature selected between 80 and 200 ° C, preferably between 90 and 185 ° C and more preferably between 100 and 175 ° C and a crystallization time that can be between 6 hours and 50 days preferably between 1 and 35 days, and more preferably between 2 and 25 days. It should be borne in mind that the components of the synthesis mixture can come from different sources which can vary the crystallization conditions described.

According to a particular embodiment of the process of the present invention, it is possible to add MWW crystals to the synthesis mixture, which act as seeds favoring the described synthesis, in an amount of up to 25% by weight with respect to the total amount of the oxides corresponding to the sources of X and Y introduced in the synthesis medium. These crystals can be added before or during the crystallization process.

According to the described process, after the crystallization described in ii), the resulting solid is separated from the mother liquor and recovered. The recovery step iii) can be carried out by different separation techniques known as for example decantation, filtration, ultrafiltration, centrifugation or any other solid-liquid separation technique and combinations thereof.

The process of the present invention may further comprise the removal of the organic content contained within the material by any known removal / extraction technique.

According to a particular embodiment, the removal of the organic compound contained inside the material can be carried out by means of a heat treatment at temperatures above 25 ° C, preferably between 100 and 1000 ° C and for a period of time preferably between 2 minutes and 25 hours

According to another particular embodiment, the material produced according to the present invention can be pelletized using any known technique.

According to a preferred embodiment, any cation present in the material can be exchanged by ion exchange for other cations using conventional techniques. Thus, depending on the X2O3 / YO2 molar ratio of the synthesized material, any cation present in the material can be exchanged, at least in part, by ion exchange. Said cations may preferably be selected from metals, protons, proton precursors and mixtures thereof, and more preferably the exchange cation is a metal selected from rare earths, metals from the NA, NIA, VAT, VA, IB, II B groups. , II IB, IVB, VB, VIB, VIIB, VIII and combinations thereof.

According to a particular embodiment, the metal could be selected from copper, iron, palladium, platinum, rhodium, gold, silver, iridium, ruthenium, osmium, and combinations thereof; preferably, they are selected from copper, iron, palladium, platinum, rhodium, and combinations thereof; and more preferably, between copper, iron, palladium and combinations thereof.

According to a preferred embodiment, any metal selected from rare earths, metals of the groups NA, NIA, IVA, VA, IB, IIB, 111 B, IVB, VB, VIB, VIIB, VIII and combinations thereof, may be incorporated during the crystallization stage, or by any method of post-synthetic deposition, preferably by impregnation or physical mixing. These metals can be introduced in their form cationic and / or from salts or other compounds that by decomposition generate the metal component or oxide in its appropriate catalytic form.

According to a particular embodiment, the metal incorporated during the crystallization stage or by any post-synthetic deposition method, could be selected from copper, iron, palladium, platinum, rhodium, gold, silver, iridium, ruthenium, osmium, and combinations of the same; preferably, they are selected from copper, iron, palladium, platinum, rhodium, and combinations thereof; and more preferably, between copper, iron, palladium and combinations thereof.

The present invention also relates to a zeolitic material with MWW structure obtained according to the process described above and which can have the following molar composition:

or X ₂ 0 ₃ : Y0 ₂ : p ADE01: q ADE02: r A: z H ₂ 0 where

X is a trivalent element;

And it is a tetravalent element;

A is an alkaline or alkaline earth cation;

or is in the range of 0 to 0.5, preferably between 0.003 to 0.1; and more preferably between 0.01 to 0.075.

p is in the range of 0.01 to 1, preferably between 0.01 to 0.5; and more preferably between 0.05 to 0.2.

q is in the range of 0.01 to 2, preferably between 0.05 to 1; and more preferably between 0.1 to 0.6.

r is in the range of 0 to 2, preferably 0 to 1; and more preferably between 0 to 0.8.

z is in the range of 0 to 2, preferably 0 to 1; and more preferably between 0 to 0.8.

According to a preferred embodiment, the material obtained according to the present invention can be calcined. Thus, the zeolitic material with MWW structure can have the following molar composition after being calcined:

or X2O3: Y0 ₂ : r A

where

X is a trivalent element;

And it is a tetravalent element; A is an alkaline or alkaline earth cation;

or is in the range 0 to 0.5, preferably between 0.003 to 0.1; and more preferably between 0.01 to 0.075.

In the described MWW zeolitic material, the tetravalent element Y may be selected from silicon, tin, titanium, zirconium, germanium, and combinations thereof, preferably is Si, and the trivalent element X may be selected from aluminum, boron, iron, indium, gallium and combinations thereof, preferably between Al and B and, more preferably, Al.

In the material described above, any cation present in the material can be incorporated by ion exchange for other cations using conventional techniques. Thus, depending on the X2O3 / YO2 molar ratio of the synthesized material, any cation present in the material can be exchanged, at least in part, by ion exchange. These exchange cations are preferably selected from metals, protons, proton precursors (such as ammonium ions) and mixtures thereof, more preferably said cation is a metal selected from rare earths, metals from the NA, NIA, VAT, VA groups , IB, IIB, 111 B, IVB, VB, VIB, VIIB, VIII and combinations thereof, and subsequently heat treated.

In the material described above, any metal selected from rare earths, metals of the groups NA, NIA, IVA, VA, IB, IIB, IIIB, IVB, VB, VIB, VIIB, VIII and combinations thereof can be incorporated during the crystallization stage, by exchange (if applicable), and / or by impregnation or by physical mixing. These metals can be introduced in their cationic form and / or from salts or other compounds, such as organometallic complexes, which by decomposition generate the metal component or oxide in its appropriate catalytic form.

According to a particular embodiment, the incorporated metal could be selected from copper, iron, palladium, platinum, rhodium, gold, silver, iridium, ruthenium, osmium, and combinations thereof; preferably, they are selected from copper, iron, palladium, platinum, rhodium, and combinations thereof; and more preferably, between copper, iron, palladium and combinations thereof.

The present invention also relates to the use of the materials described above and obtained according to the synthesis process of the present invention as catalysts for the conversion of feeds formed by organic compounds into products of higher added value, or as a molecular sieve for elimination. selective separation or adsorption of reactive stream components (eg gas mixtures) by contacting the feeds with the material obtained.

According to a preferred embodiment, the material obtained according to the present invention can be used as a catalyst in aromatic acylation processes, where the alkylatable aromatic compound can be selected from benzene, biphenyl, naphthalene, anthracene, phenanthrene, thiophene, benzothiophene, substituted derivatives of they and combinations thereof, and the alkylating agent is selected from defined, alcohols, polyalkylated aromatic compounds and combinations thereof. The material obtained, containing or not containing hydrogenating-dehydrogenating components, can be used in aromatic alkyl dealkylation processes, alkylaromatic transalkylation, aromatic alkyl isomerization, or in combined alkylaromatic dealkylation and transalkylation processes.

According to a preferred embodiment, the material obtained according to the present invention can be used as a catalyst in oligomerization processes of light strips, such as propene, butene, or pentene, for the production of synthetic liquid fuels, within the range of gasoline or from diesel.

According to a preferred embodiment, the material obtained according to the present invention can be used as a catalyst in linear hydrocarbon isomerization processes, such as in butene isomerization processes, in n-paraffin isomerization processes belonging to the naphtha fraction, or in isomerization processes of long-chain n-paraffins (dewaxing or isodewaxing processes). According to a preferred embodiment, the material obtained according to the present invention can be used as a catalyst in hydrocarbon cracking processes, or in processes of converting methanol to light olefins and / or hydrocarbons.

According to another preferred embodiment, the material obtained in the present invention can be used as a catalyst in selective catalytic reduction (RCS) reactions of NOx (nitrogen oxide) in a gas stream. In particular, the NOx RCS will be performed in the presence of reducing agents, such as ammonium, urea and / or hydrocarbons. Materials to which copper atoms have been introduced according to any of the known techniques are especially useful for this use.

According to another preferred embodiment, the material obtained in the present invention can be used as a passive adsorbent to treat the exhaust gases of an internal combustion engine, which comprises the adsorption of NOx at low temperatures, preferably less than 200 ° C, and its subsequent thermal desorption at temperatures higher than adsorption, the elimination of desorbed NOx being possible in a catalyst located after the passive adsorbent, preferably in an RCS catalyst.

Throughout the description and the claims the word "comprises" and its variants are not intended to exclude other technical characteristics, additives, components or steps. For those skilled in the art, other objects, advantages and features of the invention will be derived partly from the description and partly from the practice of the invention.

The present invention is illustrated by the following examples that are not intended to be limiting thereof.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1: Diffraction patterns of the materials obtained in Examples 2 and 3 of the present invention.

Figure 2: TEM images of the synthesized materials according to Examples 2 and 3 of the present invention.

Figure 3: NOx adsorption-desorption using the material synthesized according to Examples 4 and 5 of the present invention. EXAMPLES

Example 1: Synthesis of ADEO / V-butyl- / V-methylhexamethylene ammonium (BMH)

The synthesis of the iodide of A / -butyl-A / -methylhexamethylene thionium (BMH) is described below.

The 1-bromobutane reagent (60.88 g; 0.445 mol) is added dropwise to a solution of hexamethyleneimine (44.14 g; 0.444 mol) in anhydrous dimethylformamide (250 ml) under an inert atmosphere, maintaining vigorous stirring. Subsequently, the mixture is heated to 70 ° C and allowed to react for 16 h. The mixture is then allowed to cool and a white crystalline solid corresponding to the / V-butylhexamethylene ammonium bromide salt is formed, which is filtered off under reduced pressure. The crystals are washed to remove dimethylformamide residues and dried under reduced pressure and heat. Then, said salt (50.39 g; 0.213 mol) is dissolved in 400 ml of water, anhydrous Na2CC> 3 (22.61 g; 0.213 mol) is added and allowed to react at room temperature under strong stirring. As the reaction proceeds, a biphasic mixture forms. The resulting mixture is transferred to a separatory funnel, and the phases are separated, the organic phase being reserved. Said organic phase is washed with a saturated NaCl solution (100 ml) and subsequently dried with anhydrous MgSCU and filtered to separate the inorganic salt. N-Butylhexamethyleneimine is obtained as a colorless dense liquid.

Then, the / V-butylhexamethyleneimine (21.84 g; 0.141 mol) is dissolved in 200 ml of chloroform, the solution obtained being cooled in an ice bath. Once the solution reaches 0 ° C, iodomethane (39.91 g; 0.281 mol) is added dropwise. When the system reaches room temperature, it is allowed to react for 72 h. After the reaction is over, the solvent is mostly evaporated and ethyl acetate is added to precipitate the compound. The / V-butyl-A / - methylhexamethylene ammonium (BMH) iodide is obtained as a white solid.

Example 2: Synthesis of MCM-22 Nanocrystalline Zeolite (nMVWV)

In a first step, 231 mg of sodium aluminate (NaAIC>2; 58.9% AI2O ₃ , 38.7% Na ₂ 0, 2.4% H2O, Cario Erba) are dissolved in 1783 mg of an aqueous solution of sodium hydroxide (NaOH, 20% in water) and, subsequently, 30.9 g of milliQ water are added. Once the mixture is homogeneous, 1190 mg of BM H is added, the synthesis of which has been described in Example 1. Next, 1600 mg of hexamethyleneimine (99% HMI, Sigma Aldrich) is added, and the resulting mixture is left. minutes in agitation Finally, 2400 mg of smoked silica (particle size = 0.007 pm, Sigma Aldrich) is added, and the mixture is kept under stirring for one hour to obtain a homogeneous gel. The final composition of the gel is: S1O2: 0.042 AI2O3: 0.15 Na ₂ 0: 0.1 BMH: 0.4 HMI: 45 H2O. The gel is introduced into a steel autoclave coated with a Teflon sheath, and kept at 150 ° C for 7 days. After this period of time, the resulting solid is washed with plenty of distilled water and acetone, and dried at 90 ° C overnight. X-ray diffraction confirms that the solid obtained has the characteristic peaks of the MCM-22 zeolite, MWW structure (see Example 2 in Figure 1).

The organic matter occluded inside the pores of the MWW structure is removed by a calcination stage with air at 550 ° C for 8 hours. The acid form of the material is obtained by cation exchange using a 1.0 M solution of NH4CI (1.0 g sample: 10 ml solution) at 80 ° C for 3 hours. The sample is filtered and washed with distilled water and acetone, and calcined in air at 350 ° C for 4 hours.

The chemical composition of the final sample has an Si / Al ratio of 11.1. The textural properties of the synthesized material according to Example 2 of the present invention have been calculated by adsorption / desorption of N2, obtaining 483 m ² / g, 358 m ² / g, and 125 m ² / g, for the total BET area , micropore area and external area, respectively. The material synthesized according to Example 2 has nanocrystals with average sizes around 50-90 nm in the crystallographic directions [100] and [010] (see Example 2 in Figure 2).

Example 3: Synthesis of conventional MCM-22 zeolite (MWW) (comparative example)

231 mg of sodium aluminate (NaAIC>₂; 58.9% AI ₂ O ₃ , 38.7% Na ₂ 0, 2.4% H2O, Cario Erba) are dissolved in 1783 mg of an aqueous solution of sodium hydroxide (NaOH, 20% in water) and, subsequently, 30.9 g of milliQ water are added. Next, 2000 mg of hexamethyleneimine (99% HMI, Sigma Aldrich) is added to the above solution, and the resulting mixture is left under stirring for 15 minutes. Finally, 2400 mg of smoked silica (particle size = 0.007 pm, Sigma Aldrich) is added, and the mixture is kept under stirring for one hour to obtain a homogeneous gel. The final composition of the gel is: S1O ₂ : 0.042 AI ₂ O ₃ : 0.15 Na ₂ 0: 0.5 HMI: 45 H ₂ O. The gel is introduced into a steel autoclave coated with a Teflon sheath, and kept at 150 ° C under rotation at 60 rpm for 7 days. After this period of time, the resulting solid is washed with plenty of distilled water and acetone, and dried at 90 ° C overnight. X-ray diffraction confirms that the solid obtained has the characteristic peaks of the MCM-22 zeolite, MWW structure (see Example 3 in Figure 1).

The organic matter occluded inside the pores of the MWW structure is removed by a calcination stage with air at 550 ° C for 8 hours. The acid form of the material is obtained by cation exchange using a 1.0 M solution of NH4CI (1.0 g sample: 10 ml solution) at 80 ° C for 3 hours. The sample is filtered and washed with distilled water and acetone, and calcined in air at 350 ° C for 4 hours. The chemical composition of the final sample has a Si / Al ratio of 10.6. The textural properties of the synthesized material according to Example 3 of the present invention have been calculated by adsorption / desorption of N2, obtaining 457 m ² / g, 374 m ² / g, and 83 m ² / g, for the total BET area , micropore area and external area, respectively. The material synthesized according to Example 3 has flat crystals of hexagonal symmetry with average sizes around 250-300 nm in the crystallographic directions [100] and [010] (see TEM image in Figure 2).

Example 4: Preparation of Pd-nMWW material by cation exchange

50 mg of tetraaminopaladium (ll) monohydrate chloride are dissolved

[(NH ₃ ) 4PdCl ₂ -H ₂ 0, Sigma-Aldrich] in 100 ml of water. Subsequently, 2.0 g of the nMWW material synthesized according to Example 2 of the present invention is added to the previous solution, while stirring the mixture at room temperature for 40 hours. After this time, the solid is filtered and washed with plenty of water and acetone, drying at 60 ° C. Finally, the solid is calcined at 550 ° C in air for 5 hours.

Example 5: Preparation of Pd-MWW material by cation exchange (comparative example)

50 mg of tetraaminopaladium (ll) monohydrate chloride are dissolved

[(NH ₃ ) ₄ PdCÍ ₂ -H ₂ 0, Sigma-Aldrich] in 100 ml of water. Subsequently, 2.0 g of the MWW material synthesized according to Example 3 of the present invention is added to the previous solution, while stirring the mixture at room temperature for 40 hours. After this time, the solid is filtered and washed with plenty of water and acetone, drying at 60 ° C. Finally, the solid is calcined at 550 ° C in air for 5 hours. Example 6: Preparation of Cu-nMWW material by cation exchange

The sample synthesized and calcined according to the method set forth in Example 2, is washed with 150 g of a 0.04 M aqueous solution of sodium nitrate (NaNCh, Fluka, 99% by weight) per gram of zeolite.

Then, 33.6 mg of copper acetate [(CFLCOO ^ Cu-F ^ O, Probus, 99%) is dissolved in 30 g of water, and 303 mg of the previously washed zeolite are added. The suspension is kept under stirring for 24 h. After this time the product obtained is recovered by filtration and washed with plenty of water. Finally, the material is calcined in air at 550 ° C for 4h.

Example 7: Catalytic test for the reaction of alkylation of benzene with propylene using the materials synthesized according to Examples 2 and 3.

The materials synthesized according to Examples 2 and 3 have been screened by selecting the particle size between 0.25 and 0.42 mm, to carry out the alkylation reaction of benzene with propylene. The samples (0.050 g) are diluted with silicon carbide (0.59-0.84 mm) to a total catalytic bed volume of 3.6 ml. The diluted catalysts are introduced into a 1 cm diameter steel tubular reactor, and activated at a nitrogen flow (100 ml / min) at 200 ° C for 2 hours. Then, the temperature is lowered to the reaction temperature of 125 ° C in N2 flow, the N2 flow is interrupted and a mixture of benzene: n-octane (15: 1 weight ratio) is fed until a pressure is achieved 3.5 MPa The n-octane is used as an internal standard and is inert in the experimental conditions used. At this point, the reactor is isolated to feed a mixture of benzene: n-octane (655 ml / min) and propylene (165 ml / min), the benzene / propylene molar ratio being 3.5, by parallel conduction until a composition is achieved constant, at which time the feed is passed through the reactor again, and the reaction is considered to be the beginning. Under these experimental conditions the space velocity, WHSV (Weight Hour Space Velocity) referred to propylene, is 100 h ¹ , and benzene is in the liquid phase. The composition of the current at the outlet of the reactor has been analyzed by gas chromatography in a Varian 450 connected in line, equipped with a 5% phenyl-95% dimethylpolysiloxane capillary column and with a flame ionization detector (FID). The catalytic results obtained with the materials synthesized according to Examples 2 and 3 of the present invention are shown in Table 1.

Table 1. Conversion of propylene (X,%) and yield to products (isopropylbenzene, R _{| PB} , diisopropylbenzene, R _DipB , and triisopropylbenzene, RTIPB,% weight) obtained in the alkylation reaction of benzene with propylene, using as catalyst the materials prepared according to the catalysts synthesized in Examples 2 and 3 of the present invention.

Comparing the results of the materials presented in Table 1, it is concluded that the catalyst based on the nanocrystalline MWW zeolite obtained according to Example 2 of the present invention is much more active than the conventional MWW zeolite based catalyst used for comparative purposes (see Example 3). Thus, the propylene conversions for catalysts based on the nanocrystalline MWW zeolite and conventional MWW zeolite are 96.3 and 57.5% at a reaction time (TOS, Time On Stream) of 27 and 21 min, respectively. On the other hand, the catalyst based on the material obtained according to Example 2 produces higher yield to the alkylation product, isopropylbenzene (IPB). Example 8: NOx Adsorption / Desorption using the materials synthesized according to Examples 4 and 5.

A gas stream of 500 ml / min, consisting of 60 ppm NO, 5% vol CO2, 10% vol O2, 5% vol H2O, and the remainder N2, is passed over 100 mg of the prepared Pd-nWW and PdMWW catalysts according to Examples 4 and 5 of the present invention, respectively, at the selected adsorption temperature (100 ° C) for 5 minutes. This adsorption step is followed by a desorption at a programmed temperature using a temperature ramp of 17 ° C / minute in the presence of the same gas stream, until a temperature of 450 ° C is reached.

The NOx adsorption / desorption results using the Pd-nMWW and Pd-MWW catalysts as a function of temperature are summarized in Figure 3. The total amount of NOx exorbed is 44.1 and 26.6 pmol of NOx / gram of catalyst for Pd-nMWW and Pd-MWW materials, respectively. These results allow to conclude that the material synthesized according to Example 4 of the present invention has a higher adsorption / desorption capacity of NOx than the material based on a conventional MWW zeolite used for comparative purposes (see Example 5).

Example 9: Catalytic test for the reaction of RCS of NOx using the material synthesized according to Example 6.

The catalytic activity of the Cu-nMWW sample synthesized according to Examples 6 of the present invention has been evaluated for the selective catalytic reduction (RCS) of NOx. The synthesized material has been screened by selecting the particle size between 0.25 and 0.42 mm, 100 mg of said sample being diluted in silicon carbide (0.59-0.84 mm) to a total catalytic bed volume of 1.5 ml. The diluted catalyst is introduced into a tubular steel reactor 1.2 cm in diameter and 20 cm long, and is activated in nitrogen flow (100 ml / min) at 550 ° C for 1 hour. Then, the reaction mixture (300 ml / min, 500 ppm NO, 530 ppm NH ₃ , 7% O2 and 5% H2O) is introduced, and the reaction is evaluated in the temperature range between 350-550 ° C. The NOx present at the outlet of the gases from the reactor is analyzed continuously by means of a chemiluminescent detector (Thermo 62C).

The catalytic results of the catalyst prepared according to Example 6 of the present invention are summarized in Table 2. Table 2: Conversion (%) of NOx at different temperatures (350, 400, 450, 500 ° C) using the catalyst prepared according to Example 6 of the present invention.

Claims

1. Method of synthesis of a zeolitic material with the MWW structure in its nanocrystalline form, characterized in that it comprises at least the following steps:

i) Preparation of a mixture comprising at least one source of water, at least one source of a tetravalent element Y, at least one source of a trivalent element X, at least one source of an alkaline or alkaline earth cation (A), and at least two organic molecules (ADE01 and ADE02),

where ADE01 is selected from a monocyclic quaternary ammonium where at least one of the substituents is a linear alkyl chain consisting of 3-6 carbon atoms, and ADE02 is selected from any amine or ammonium capable of directing the synthesis to crystallization of a MWW zeolite with the molar composition of the mixture being:

/ X ₂ 0 ₃ : Y0 ₂ : m ADE01: n ADE02: a A. and H ₂ 0 where

/ is in the range of 0 to 0.5

m is in the range of 0.01 to 1

n is in the range of 0.01 to 2

a is in the range of 0 to 2

z is in the range of 2 to 200

ii) Crystallization of the mixture obtained in i) in a reactor

iii) Recovery of the crystalline material obtained in ii).

2. Synthesis method according to claim 1, characterized in that the source of the tetravalent element Y is selected from silicon, tin, titanium, zirconium, germanium, and combinations thereof.

3. Synthesis method according to claim 2, characterized in that the source of the tetravalent element Y is a source of silicon selected from silicon oxide, silicon halide, colloidal silica, smoked silica, tetraalkylortosilicate, silicate, silicic acid, a previously synthesized material crystalline, a previously synthesized amorphous material and combinations thereof.

4. Synthesis method according to claim 3, characterized in that the source of silicon is selected from a previously synthesized crystalline material, a previously synthesized amorphous material and combinations thereof.

5. Synthesis method according to claim 4, characterized in that the previously synthesized materials contain other heteroatoms in their structure.

6. Synthesis method according to claim 1, characterized in that the source of the trivalent element X is selected from aluminum, boron, iron, indium, gallium and combinations thereof.

7. Synthesis method according to any of claims 1 to 6, characterized in that the zeolitic material with MWW structure is selected from materials MCM-22, ERB-1, SSZ-25, ITQ-1, or any of its disorganized variants and / or pilareadas, any of its delaminated variants, and combinations thereof.

8. Synthesis method according to claim 7, characterized in that the zeolitic material with MWW structure is MCM-22.

9. Synthesis method according to claim 1, characterized in that the ADE01 quaternary ammonium is selected from a monocyclic quaternary ammonium with the RiF CicloNT structure, wherein the Cycle group is formed between 4-8 carbon atoms, and the Ri and R _{2 groups} they are linear alkyl chains between 1-4 and 3-6 carbon atoms, respectively.

10. Synthesis process according to claim 9, characterized in that said ADE01 is selected from alkyl-pyrrolidiniums, alkyl-piperidiniums, alkyl-hexamethylene ammoniums, alkyl-heptamethylene ammoniums and combinations thereof.

11. Synthesis process according to claim 10, characterized in that said ADE01 is an alkyl hexamethylene ammonium.

12. Synthesis method according to claim 11, characterized in that said ADE01 is / \ / - butyl - / \ / - methylhexamethylene ammonium.

13. Synthesis method according to claim 1, characterized in that the organic molecule ADE02 is selected from primary, secondary or tertiary amines, diamines or polyamines, or quaternary ammoniums, diamonds or polyammoniums and combinations thereof.

14. Synthesis method according to claim 13, characterized in that ADE02 is selected from pyrrolidines, piperidines, hexamethyleneimines, heptamethyleneimines, pyrrolidiniums, piperidiniums, hexamethylene ammoniums, heptamethylene ammoniums, their alkylated derivatives, and combinations thereof.

15. Synthesis method according to claim 14, characterized in that ADE02 is pyrrolidine, piperidine, hexamethyleneimine and combinations thereof.

16. Synthesis method according to claim 15, characterized in that ADE02 is hexamethyleneimine.

17. Synthesis method according to any of the preceding claims, characterized in that the crystallization step described in ii) is carried out in an autoclave, under static or dynamic conditions.

18. Synthesis method according to any of the preceding claims, characterized in that the crystallization process described in ii) is carried out at a temperature between 80 and 200 ° C.

19. Synthesis method according to any of the preceding claims, characterized in that the crystallization time of the process described in ii) is between 6 hours and 50 days.

20. Synthesis method according to any of the preceding claims, characterized in that it further comprises adding MWW crystals as seeds to the synthesis mixture in an amount up to 25% by weight with respect to the total amount of oxides.

21. Synthesis method according to claim 20, characterized in that the MWW crystals are added before the crystallization process or during the crystallization process.

22. Synthesis method according to any of the preceding claims, characterized in that the recovery step iii) is carried out with a separation technique selected from decantation, filtration, ultrafiltration, centrifugation and combinations thereof.

23. Synthesis method according to any of the preceding claims, characterized in that it further comprises the elimination of the organic content contained within the material.

24. Synthesis process according to claim 23, characterized in that the process of eliminating the organic content contained inside the material is carried out by means of a heat treatment at temperatures between 100 and 1000 ° C for a period of time between 2 minutes and 25 hours.

25. Synthesis method according to any of the preceding claims, characterized in that the material obtained is pelletized.

26. Synthesis method according to any of the preceding claims, characterized in that any cation present in the material can be exchanged by ion exchange for other cations using conventional techniques.

27. Synthesis method according to claim 26, characterized in that the exchange cation is selected from metals, protons, proton precursors and mixtures thereof.

28. Synthesis method according to claims 26 and 27, characterized in that the exchange cation is a metal selected from rare earths, metals of the NA, NIA, IVA, VA, IB, IIB, II IB, IVB, VB, VIB groups , VIIB, VIII and combinations thereof.

29. Synthesis method according to claim 28, characterized in that the exchange cation is selected from copper, iron, palladium, platinum, rhodium, gold, silver, iridium, ruthenium, osmium, and combinations thereof.

30. Synthesis method according to claim 29, characterized in that the exchange cation is copper, iron, palladium and combinations thereof.

31. Synthesis method according to any of claims 1 to 25, characterized in that any metal selected from rare earths, metals of the groups NA, NIA, IVA, VA, IB, IIB, II IB, IVB, VB, VIB, VIIB, VIII and combinations thereof, can be incorporated during the crystallization stage, or by any method of post-synthetic deposition.

32. Synthesis method according to claim 31, characterized in that the metal is selected from copper, iron, palladium, platinum, rhodium, gold, silver, iridium, ruthenium, osmium, and combinations thereof.

33. Synthesis method according to claim 32, characterized in that the metal is selected from copper, iron, palladium and combinations thereof.

34. Zeolitic material with MWW structure obtained according to the method described in any of claims 1 to 33, characterized in that it has the following molar composition

or X ₂ 0 ₃ : Y0 ₂ : p ADE01: q ADE02: r A: z H ₂ 0 where

X is a trivalent element;

And it is a tetravalent element;

A is an alkaline or alkaline earth element;

or is in the range of 0 to 0.5;

p is in the range of 0.01 to 1;

q is in the range of 0.01 to 2;

r is in the range of 0 to 2;

z is in the range of 0 to 2.

35. Zeolitic material with MWW structure according to claim 34, characterized in that it further comprises a metal selected from rare earths, metals of the groups NA, NIA, IVA, VA, IB, IIB, II IB, IVB, VB, VIB, VIIB, VIII and combinations thereof.

36. Zeolitic material with MWW structure according to claim 35, characterized in that it further comprises a metal selected from copper, iron, palladium, platinum, rhodium, gold, silver, iridium, ruthenium, osmium, and combinations thereof.

37. Zeolitic material with MWW structure according to claim 36, characterized in that the metal is selected from copper, iron, palladium and combinations thereof.

38. Zeolitic material with MWW structure according to claim 34, characterized in that it has the following molar composition after being calcined:

or X ₂ 0 ₃ : Y0 ₂ : r A

where

X is a trivalent element;

And it is a tetravalent element; Y

A is an alkaline or alkaline earth element;

or is in the range 0 and 0.5;

rest is in the range of 0 to 2.

39. Zeolitic material with MWW structure according to any of claims 34 to 38, characterized in that the tetravalent element Y is selected from silicon, tin, titanium, zirconium, germanium, and combinations thereof.

40. Zeolitic material with MWW structure according to claim 39, characterized in that the tetravalent element Y is silicon.

41. Zeolitic material with MWW structure according to any of claims 34 to 38, characterized in that the trivalent element X is selected from aluminum, boron, iron, indium, gallium and combinations thereof.

42. Zeolitic material with MWW structure according to claim 41, characterized in that the trivalent element X is aluminum.

43. Zeolitic material with MWW structure according to any of the preceding claims, characterized in that the size of the crystals of said zeolitic material along the crystallographic directions [100] and [010] is in the range of 10 to 100 nm, and along the crystallographic direction [001] is in the range of 2 to 50 nm.

44. Use of a zeolitic material with MWW structure described in any of claims 34 to 43 and obtained according to the synthesis procedure described in any of claims 1 to 33 in processes for the conversion of certain feed components formed by organic compounds into products of greater added value, or for their elimination and / or selective adsorption of a reactive current by contacting said feed with the described material.

45. Use of a zeolitic material with MWW structure according to claim 44, for the revaluation of currents rich in aromatic compounds by processes of alkylation, dealkylation, transalkylation, isomerization and combinations thereof.

46. Use of a zeolitic material with MWW structure according to claim 44, for the production of synthetic liquid fuels, within the range of gasoline or diesel, after contacting said material with light strips under certain reaction conditions.

47. Use of a zeolitic material with MWW structure according to claim 44, for the revaluation of streams rich in linear paraffins by isomerization, hydroisomerization processes and combinations thereof.

48. Use of a zeolitic material with MWW structure according to claim 44, for the production of light shafts by catalytic cracking processes.

49. Use of a zeolitic material with MWW structure according to claim 44 for the conversion of methanol to light weight and / or hydrocarbons.

50. Use of a zeolitic material with MWW structure according to claim 44 for the selective catalytic reduction (RCS) of NOx (nitrogen oxide) in a gas stream.

51. Use of a zeolitic material with MWW structure according to claim 44 as a passive NOx adsorbent at temperatures below 200 ° C, and subsequently capable of desorbing said NOx at temperatures above 200 ° C.