Aromatization catalyst with high KL zeolite content

Abstract

The present invention relates to a method for preparing an aromatization catalyst comprising at least 70% KL zeolite, a refractory oxide of silica (SiO2), and a Group VIIIB metal, which comprises hydrothermally treating the support in the presence of steam. The present invention also relates to the specific support obtained, the aromatization catalyst, and a method for aromatizing at least one alkane or cycloalkane contained in a hydrocarbon feedstock comprising a C6-C8 paraffin fraction using the aromatization catalyst.

Description

[Technical Field]

[0001] The present invention relates to a catalyst consisting of a microporous material in the form of extrudates, tablets or beads containing at least 70% by weight of KL zeolite (structure type LTL) in a binder consisting of at least one silica source. [Background technology]

[0002] Zeolite is SiO4 4- and AlO4 5- It is a crystalline aluminosilicate material with organized microporosity formed by a three-dimensional arrangement of tetrahedra, and therefore offers a wide variety of structures. The International Zeolite Association (IZA) has created a classification of zeolites according to their structure (structure type). Zeolites are widely used in industry for adsorption, separation, catalysis, or ion exchange. KL zeolite is a zeolite of the LTL structure type, which contains a one-dimensional microporous system with pore openings of 12T atoms (T is silicon or aluminum). The cations to compensate for the charge of the structure are K + As used in industrial processes, zeolites are shaped to give objects with a size larger than the zeolite crystals, thus facilitating their handling and the passage of feedstock through reactors. It is very difficult to shape pure KL zeolite to obtain a product with good mechanical strength. Generally, to obtain shaped objects containing a high proportion of KL zeolite, conventional methods use clay, alumina, or silica, which are mixed with the zeolite for shaping. The properties of the selected binder affect not only the mechanical strength of the catalyst, but also its catalytic performance.

[0003] The preparation of catalysts from KL zeolite in the presence of silica is known practice.

[0004] Patent document 1 presents, inter alia, a method for obtaining a shaped material containing KL zeolite. The method involves mixing KL zeolite with a source of silica or pseudoboehmite and then shaping the mixture by a combination of mixing and extrusion. Aluminum nitrate is added to improve the water sensitivity (WSI = water sensitivity index) of the catalyst.

[0005] Patent Document 2 presents a method for obtaining a shaped material containing KL zeolite. The method involves mixing KL zeolite with silica and then shaping the mixture by a combination of mixing and extrusion. The percentage of KL zeolite relative to the total weight of KL zeolite and silica is 83%. Platinum and one or more halide compounds are subsequently applied. The patent presents a catalyst with improved performance when the XANES peak of Pt exhibits an intensity of 0.4 or more and when the dealumination rate obtained is 3% or more. No textural data is provided.

[0006] Patent Document 3 presents a method for obtaining a shaped material containing KL zeolite. The method involves mixing KL zeolite with silica and Methocel® and then shaping the mixture by a combination of mixing and extrusion. The percentage of KL zeolite relative to the total mass of KL zeolite and silica is 83%, and a single silica source, a colloidal sol, is used. The preparation of the catalyst support further requires numerous washing operations to remove residual alkali resulting from the silica precursor and processing aids. Fluorine- or chloride-based halogen compounds are used. The patent does not present any data regarding the mechanical strength of the resulting extrudates. Catalysts impregnated on washed materials exhibit better stability with improved cycle times.

[0007] Patent document 4 presents a shaped material in the form of extrudates containing KL zeolite and silica. The mechanical strength of the resulting extrudates is greater than 3 lb / mm (1.3 daN / mm). This improved mechanical strength is due to the use of zeolite in the form of agglomerates with a size of 1.4 μm to 6 μm. Furthermore, this method requires the use of halogen compounds of the fluorine or chloride type.

[0008] Patent application WO 02 / 04999 describes the preparation of a catalyst for aromatizing the C6-C8 fraction, which comprises KL zeolite, a binder (silica in the examples), platinum, and a halide. The patent indicates that if some of the intermediate calcination steps are omitted, the catalyst retains the same performance as a catalyst prepared under standard conditions by a preparation method including three calcination steps.

[0009] Patent document 6 relates to a platinum catalyst on a KL zeolite and refractory oxide type support, and the preparation method includes a washing step to enrich the catalyst with K or Cs. The catalyst has a micropore volume of 0.015-0.05 cc / g and an SBET of 100-170 m 2 / g. It also contains chlorine and fluorine.

[0010] Patent document 7 describes a regenerable catalyst containing a zeolite, preferably KL, and a binder, the zeolite preferably being exchanged with barium, and characterized by a high SBET and a high pore volume, according to a preparation protocol involving ion exchange of the zeolite.

[0011] The catalysts for aromatization of the C6-C8 fraction described in the prior art essentially consist of a zeolite (preferably KL) formed in a siliceous binder. The active metal can be platinum. Various preparation methods have been reported: ion exchange of the KL zeolite, or the presence of a washing operation (to reduce the Na content), or the presence of a halogen compound. The support and catalyst are subjected to one or more heat treatments of the calcination type.

[0012] For aromatization of the C6 / C8 fraction, silica has been found to be the best choice of binder in terms of catalytic performance. Silica is more neutral in nature than alumina. Alumina-type binders have more OH sites than silica, which promotes cracking reactions, which are undesirable.

[0013] Silica is an advantageous compound for use as a catalyst support, but it is known that silica cannot be extruded like other materials in conventional extrusion equipment to produce a product that is sufficiently resistant to use in the process. This is because, from its production to its use, the catalyst faces numerous steps that can have an impact on its physical integrity. It must be particularly resistant to spallation, abrasion, and pressure fluctuations associated with the operating conditions of the catalytic reactor in which it is used. As a result, there is a continuing need for high-performance catalysts with improved mechanical and physical properties. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] U.S. Patent No. 4,830,732 [Patent Document 2] U.S. Patent No. 5,354,933 [Patent Document 3] U.S. Patent No. 6,207,042 [Patent Document 4] U.S. Patent No. 8,263,518 [Patent Document 5] International Publication No. 2019 / 217054 [Patent Document 6] US Patent Application Publication No. 2018 / 169638 [Patent Document 7] U.S. Patent Application Publication No. 2014 / 008833 Summary of the Invention [Means for solving the problem]

[0015] (Summary of the Invention) The Applicant has surprisingly found that a particular preparation method, in particular using a hydrothermal treatment in the presence of steam on a support based on refractory oxides of the SiO type and KL zeolite prior to impregnation with a Group VIII metal, results in an aromatization catalyst with improved catalytic properties and good mechanical strength. The method according to the invention further exhibits the advantages of being more environmentally friendly, avoiding water-consuming washing operations and avoiding the use of harmful halides.

[0016] The present invention relates to a process for preparing an aromatization catalyst comprising at least 70% by weight of KL zeolite, a refractory oxide of the SiO2 silica type and a Group VIIIB metal, the process comprising at least the following steps: a) mixing at least one source of KL zeolite of structural type LTL and at least one source of SiO2 silica in at least one solvent selected from water, physical solvents and chemical solvents, optionally in the presence of an organic adjuvant; to obtain a mixture; b) shaping the mixture resulting from step a), preferably by extrusion; c) optionally aging the shaped material in air, preferably in humid air with a relative humidity of 20% to 100%, at a temperature of 0 to 70°C for a period of 1 minute to 72 hours; d) optionally drying the shaped and optionally aged material at a temperature between 0 and 200°C for a period between 1 minute and 72 hours; optionally followed by a step d') of calcination at a temperature between 200 and 600°C, preferably between 250 and 450°C, for a period between 1 and 12 hours, preferably between 1 and 4 hours; e) hydrothermally treating the material shaped in step b), optionally aged in step c) and optionally dried / calcined in step d) in the presence of water vapor at a temperature of 200-550°C, preferably at atmospheric pressure, for a period of 30 minutes to 5 hours; to obtain a catalyst support; f) calcining the support resulting from step e) at a temperature of 200 to 680°C, preferably 400 to 660°C, for a period of 1 to 12 hours, preferably 1 to 4 hours; to obtain a calcined catalyst support; g) impregnation with a group VIII metal, preferably platinum, by contacting the support obtained as a result of step e) or f) with a solution of a precursor of said metal dissolved in an aqueous phase, so that the metal content on the catalyst is between 0.1% and 10% by weight, preferably between 0.2% and 5% by weight, preferentially between 0.3% and 2% by weight, and very preferentially between 0.5% and 1.2% by weight, relative to the total mass of the anhydrous catalyst; h) drying the impregnated material resulting from step g), preferably at a temperature between 50°C and 200°C; i) calcining the dried material resulting from step h) in a gas stream of either pure air or air diluted with a neutral gas at a temperature between 200°C and 500°C, preferentially between 250°C and 450°C, very preferentially between 350°C and 420°C; to give a calcined catalyst.

[0017] The preparation method may include: j) reducing the calcined catalyst resulting from step i), by contacting the catalyst with a gas stream containing hydrogen, either pure or diluted with a neutral gas, at a temperature between 300°C and 550°C, preferentially between 350°C and 500°C, and very preferentially between 450°C and 500°C, before contacting it with the feedstock.

[0018] Step a) may be carried out by mixing at room temperature for a period of 5 to 60 minutes, preferably 10 to 50 minutes.

[0019] The KL zeolite and SiO2 silica are used in step a) as a mixture of oxides in the following proportions: - at least one KL zeolite; 70% to 90% by weight, preferably 70% to 85% by weight, and - at least one source of SiO2 silica; from 10% to 30% by weight, preferably from 15% to 30% by weight The mixture may be introduced with: a solvent; from 10% to 30% by weight relative to the total weight of said mixture of oxides, and - at least one organic adjuvant; from 0% to 20% by weight, preferably from 1% to 15% by weight, preferentially from 1% to 10% by weight and very preferentially from 1% to 7% by weight of at least one organic adjuvant, relative to the total weight of said mixture of oxides may be mixed with The sum of the amounts of each compound introduced in this step is 100%.

[0020] A single source of silica may be used in step a), preferably precipitated silica or silica gel, very preferentially precipitated silica.

[0021] Two different silica sources may be used in step a), the two silica sources being preferably precipitated silica and colloidal silica sol.

[0022] The particle size or granulometry of the silica used in step a) may be less than 100 μm for precipitated silicas or silica gels, preferentially less than 80 μm, more preferentially less than 60 μm, even more preferentially less than 20 μm, or indeed less than 10 μm in the case of precipitated silicas or silica gels, and between 5 and 200 nm, preferentially between 15 and 50 nm in the case of colloidal silica sols.

[0023] The organic adjuvants may be selected from cellulose derivatives, polyethylene glycols, aliphatic monocarboxylic acids, alkyl aromatic compounds, sulfonates, fatty acids, polyvinylpyrrolidone, polyvinyl alcohol, methylcellulose, polyacrylates, polymethacrylates, polyisobutene, polytetrahydrofuran, starch, polysaccharide type polymers, scleroglucan, hydroxyethylcellulose type derivatives, carboxymethylcellulose (e.g., Methocel®), lignosulfonates and galactomannan derivatives, employed alone or in mixtures, preferably carboxymethylcellulose.

[0024] The specific surface area of ​​the support obtained as a result of step e) or f) is 80 to 200 m 2 / g, total pore volume 0.35-0.6cm 3 / g, macropore volume 0.08~0.16cm 3 / g, mesopore volume 0.2 cm 3 / g~0.4cm 3 / g and micropore volume 0.07 cm 3 / g, a sodium content of less than 0.2% by weight, and a mechanical strength, measured by a single pellet crushing test, hereinafter referred to as SPC, of ​​at least 0.5 daN / mm, preferably at least 0.6 daN / mm and preferentially at least 0.7 daN / mm.

[0025] The present invention also relates to a support for an aromatization catalyst in the form of a composite KL zeolite-SiO2 material containing at least 70% KL zeolite, which is obtained in step e) or f) of the process according to any of the described variants and has a specific surface area of ​​80 to 200 m 2 / g, total pore volume 0.35-0.6cm 3 / g, macropore volume 0.08~0.16cm 3 / g, mesopore volume 0.2 cm 3 / g~0.4cm 3 / g and micropore volume 0.07 cm 3 / g, a sodium content of less than 0.2 wt. %, and a mechanical strength, hereinafter referred to as SPC, measured by a single pellet crushing test of at least 0.5 daN / mm, preferably at least 0.6 daN / mm, preferably at least 0.7 daN / mm.

[0026] The present invention also relates to a catalyst for the aromatization of C6-C8 paraffin fractions, which catalyst can be prepared by a method according to any of the described variants and which comprises at least 70% by weight of KL zeolite of LTL structural type, with a Si / Al ratio between 2.8 and 4, preferably between 2.8 and 3.5, 10% and 30% by weight of a refractory oxide of SiO2 silica type, a metal of group VIIIB, preferably platinum, said catalyst having a specific surface area between 80 and 200 m 2 / g, micropore volume 0.04 cm 3 / g or less, a content of Group VIIIB metals between 0.1% and 10% by weight, preferably between 0.2% and 5% by weight, very preferentially between 0.3% and 2% by weight, even more preferentially between 0.5% and 1.2% by weight, and furthermore a dispersion of said metals between 50% and 70%.

[0027] The metal may be platinum, and the platinum content may be between 0.6% and 1.0% by weight relative to the total weight of the catalyst.

[0028] The KL zeolite content of the catalyst may be 70% to 85% by weight, the refractory oxide content of the catalyst may be 15% to 30% by weight, and the total of the catalyst components, including metals, is 100%.

[0029] The invention finally relates to a process for aromatizing at least one alkane or cycloalkane contained in a hydrocarbon feedstock containing a C6-C8 paraffin fraction, which process is carried out by contacting a catalyst prepared according to any of the described variants or a catalyst according to any of the described variants with a gaseous feedstock for treatment in the presence of hydrogen, said process being carried out in the liquid or gas phase at a temperature of 400°C to 550°C, a pressure of 2 to 20 MPa, a molar ratio of hydrogen to hydrocarbon compounds of 1 to 10, and a weight hourly space velocity (WHSV) of 1 to 10 h -1 It is operated by.

[0030] The aromatization process may exhibit a conversion of n-paraffins and isoparaffins to C6-C7 of 85% or more and a yield of aromatics of 80% or more. DETAILED DESCRIPTION OF THE INVENTION

[0031] (Description of the embodiment) The invention will be described in detail below using non-limiting embodiments and examples.

[0032] Furthermore, specific and / or preferred embodiments of the present invention are described, which can be implemented separately or together, without limitation of combinations where the combination is technically feasible.

[0033] (definition) Mass percentages are expressed relative to the anhydrous mass of the final composite (support or catalyst) unless otherwise indicated. This anhydrous mass is determined by a measurement called loss on ignition (LOI). Loss on ignition corresponds to the change in mass that results from heating a sample at 1000°C for 2 hours. Loss on ignition is expressed as a mass percentage of solids.

[0034] Throughout the remainder of the text, side crush strength is understood to mean the mechanical strength of a material (support or catalyst) according to the invention, as determined by the single-pellet crush (SPC) test. This is a standardized test (standard ASTM D4179-01) that involves subjecting a material in the form of millimeter-sized bodies, such as beads, pellets, or extrudates, to a compressive force that causes fracture. This test is therefore a measure of the tensile strength of the material. The analysis is repeated on a number of individually sampled solids, typically 10 to 200 solids. The average of the measured breaking side forces constitutes the average SPC, which is expressed in units of force (N) in the case of granules and in units of force per unit of length (daN / mm or decaNewtons per millimeter of extrudate length) in the case of extrudates.

[0035] Throughout the remainder of the text, specific surface area is understood to mean BET specific surface area (SBET), determined by nitrogen adsorption according to standard ASTM D3663-78, established from the Brunauer-Emmett-Teller method, as described in Journal of the American Chemical Society, 60, 309 (1938).

[0036] The term "macropore" means a pore with an opening greater than 50 nm.

[0037] The term "mesopore" means a pore with an opening between 2 nm and 50 nm inclusive.

[0038] The term "micropore" means a pore with an opening of less than 2 nm.

[0039] The term "total pore volume" (TPV) of a material, support or catalyst according to the invention is understood to mean the volume measured by mercury intrusion porosimetry according to standard ASTM D4284-83 at a maximum pressure of 4000 bar (400 MPa), using a surface tension of 484 dyn / cm and a contact angle of 140°. The wetting angle was taken to be equal to 140°, in accordance with the recommendation on pages 1050-1055 of the study "Techniques de l'ingenieur, traite analyse et caracterisation" written by Jean Charpin and Bernard Rasneur.

[0040] For better accuracy, the value of the total pore volume corresponds to the value of the total pore volume measured by mercury intrusion porosimetry measured on a sample minus the value of the total pore volume measured by mercury intrusion porosimetry measured on the same sample for a pressure equivalent to 30 psi (approximately 0.2 MPa).

[0041] The macropore and mesopore volumes are measured by mercury intrusion porosimetry according to standard ASTM D4284-83 at a maximum pressure of 4000 bar (400 MPa), using a surface tension of 484 dyne / cm and a contact angle of 140°. The value at which mercury fills all interparticle voids is set to 0.2 MPa, above which mercury is considered to penetrate into the pores of the sample.

[0042] The macropore volume of a material, support or catalyst according to the invention is defined as the cumulative volume of mercury introduced at a pressure between 0.2 MPa and 30 MPa, and corresponds to the volume contained in pores with an apparent diameter greater than 50 nm.

[0043] The mesopore volume of the material, support or catalyst according to the present invention is defined as the cumulative volume of mercury introduced at a pressure of 30 MPa to 400 MPa, which corresponds to the volume contained in pores with an apparent diameter of 2 nm to 50 nm.

[0044] The median macropore diameter (Dmacro (nm)) of a material, support or catalyst according to the invention is defined as the diameter such that all pores having a size less than this diameter constitute 50% of the macropore volume as measured by mercury porosimetry.

[0045] The median diameter of the mesopores (Dmeso (nm)) of a material, support or catalyst according to the invention is defined as the diameter such that all pores having a size less than this diameter constitute 50% of the mesopore volume as measured by mercury porosimetry.

[0046] The micropore volume of the material, support or catalyst is preferably determined by filtration at a temperature of 77 Kelvin (77 K) under vacuum (P<6.7×10 -4 The micropore volume is calculated via the t-plot method from the nitrogen adsorption isotherm measured at temperatures between 200 and 650 °C for a period ranging from 9 to 16 hours, preferably at 500 °C for 10 hours, after degassing to 1000 Pa. Measurement of the nitrogen adsorption isotherm at 77 Kelvin (77 K) is then carried out on an ASAP 2020 M instrument from Micromeritics, taking at least 35 measurement points at relative pressures with a ratio P / P0 between 0.002 and 1. The micropore volume is determined from the isotherm obtained by the t-plot method, applying standard ISO 15901-3:2007 and calculating the statistical thickness t via the Harkins-Jura equation. The micropore volume is obtained by linear regression from the points of the t-plot and the slope of the linear regression from the y-axis to the origin, respectively. The evaluated micropore volume is expressed as cm of liquid adsorbent per gram of anhydrous adsorbent weight. 3 It is expressed as:

[0047] The micropore volume may also allow verification of the percentage of KL zeolite present in the various steps of the process for producing the catalyst according to the invention, which as a result of the process contains a minimum of 70% by weight of KL zeolite. Pure KL zeolite has a micropore volume of 0.140 cm. 3 / g. 3A micropore volume less than 0.070 cm / g indicates the presence of amorphous material without microporosity in the material or a possible partial blockage of the zeolite microporosity. In the absence of partial blockage of the zeolite microporosity, the value for micropore volume is proportional to the amount of KL zeolite present in the mixture. For example, a micropore volume less than 0.070 cm / g indicates the presence of amorphous material without microporosity in the material or a possible partial blockage of the zeolite microporosity. In the absence of partial blockage of the zeolite microporosity, the value for micropore volume is proportional to the amount of KL zeolite present in the mixture. 3 A micropore volume of 1000 kJ / g means that the mixture contains 50% KL zeolite.

[0048] The molar amounts of the various elements present in the material may be determined by X-ray fluorescence. This method makes it possible, in particular, to determine the Si / Al ratio of the microporous zeolite material. For pure or highly purified KL zeolites, the Si / Al ratio is generally between 2.8 and 4.3, with no upper limit.

[0049] X-ray fluorescence (XRF) spectroscopy is a chemical analysis technique that uses the fluorescence of X-rays, a physical property of materials. It allows the analysis of most chemical elements, starting with beryllium (Be), in concentrations ranging from a few ppm to 100%, with accurate and reproducible results. X-rays are used to excite atoms in the sample, causing them to emit X-rays with energies characteristic of each element present. The intensity and energy of these X-rays are then measured to determine the concentrations of elements in the catalyst, particularly the Pt and Cl content.

[0050] H2O2 titration is a dynamic chemisorption measurement technique that reveals the state of dispersion of metals, particularly platinum (Pt), on the catalyst after reduction of said catalyst.

[0051] The solid is equilibrated in a stream of carrier gas (He) containing small amounts of a "probe" gas delivered in pulses. Each pulse contains a known amount of adsorbent. The amount adsorbed by the solid is measured as the difference between the proportions of the "probe" gas at the inlet and outlet of the reactor.

[0052] The analytical instrument used to perform the dynamic chemisorption is an Xorb tool (T135) from GIRA.

[0053] Titration measurements are carried out on approximately 2 g of sample after a first step of calcination in air at 400 °C / 2 h, followed by reduction in H2 at 470 °C / 2 h. After returning to room temperature, a first O2 pulse series is carried out to measure a first volume of oxygen chemisorbed on the metals, in particular platinum, of catalyst (V1), and then, after reduction at room temperature for 1 h, a second O2 pulse series is carried out to measure a second volume of oxygen chemisorbed on the metals, in particular platinum, of catalyst (V2).

[0054] The theoretical volume of oxygen consumed, assuming all metal atoms (eg, platinum atoms) are accessible, is calculated as follows:

[0055]

number

[0056] The dispersion of the metal (for example platinum) is then obtained according to the following formula:

[0057]

number

[0058] The following is true throughout the text:

[0059] The term "support" refers to a material consisting of KL zeolite (a) and a silica-type refractory oxide (b), preferably formed by mixing / extrusion.

[0060] The term "catalyst" refers to a support as defined above loaded with a Group VIIIB metal (c), such as platinum.

[0061] Within the meaning of the present invention, the different embodiments presented can be used alone or in combination with each other, without any restrictions on the combinations.

[0062] For purposes of the present invention, various ranges of parameters for a given process, such as pressure ranges and temperature ranges, can be used alone or in combination. For example, for purposes of the present invention, a preferred range of pressure values ​​can be combined with a more preferred range of temperature values.

[0063] It is an object of the present invention to propose a catalyst suitable for the aromatization of C6 / C8 or C6 / C7 hydrocarbon fractions, said catalyst comprising, in particular: (a) KL zeolite (structural type LTL); the Si / Al molar ratio is advantageously between 2.8 and 4, preferably between 2.8 and 3.5, the Si / Al molar ratio being highly preferentially 3; (b) refractory oxides of the silica type; (c) Group VIIIB metals.

[0064] The Applicant has surprisingly found that a catalyst preparation method starting from a mixture of KL zeolites and using a hydrothermal type heat treatment in the presence of water vapor in the presence of at least one synthetic silica source having a low sodium content (commonly called "steaming") results in a catalyst that, after the addition of platinum, exhibits improved performance in the aromatization of C6 / C8, in particular C6 / C7, fractions and has different textural properties relative to the catalysts of the prior art, while ensuring high mechanical strength.

[0065] The catalyst according to the invention is therefore in the form of an active phase based on KL zeolite, to which is added a refractory oxide of the SiO2 silica type which will act as a binder, constituting the support, and finally to which is added a metal of Group VIIIB, for example platinum (irrespective of the order and manner in which these various compounds are introduced), constituting the catalyst.

[0066] Preferably, the content of (b) refractory oxide in the form of silicon oxide is between 10% and 30% by weight of the support, and very preferentially between 15% and 30% by weight of the support.

[0067] Preferably, the S_BET specific surface area of ​​the support is at least 80 m 2 / g, preferably 120 to 200m 2 / g. This type of specific surface area for the catalyst support results in particularly good catalytic activity.

[0068] The KL zeolite (a) content of the catalyst is advantageously chosen to be at least 70% by weight, in particular between 70% and 85% by weight, relative to the total weight of the catalyst.

[0069] The content of refractory oxide of SiO2 type in the catalyst is between 10% and 30% by weight, preferably between 15% and 30% by weight, relative to the total weight of the catalyst.

[0070] Preferably, the group VIIIB metal (c) may be a platinum group element, in particular Pt or Pd, preferably Pt. Preferably, the content of the group VIIIB metal (c) may be 0.1% to 10% by weight, preferably 0.2% to 5% by weight, highly preferentially 0.3% to 2% by weight, even more preferentially 0.5% to 1.2% by weight, and highly advantageously 0.6% to 1.0% by weight, relative to the total weight of the catalyst. In one highly preferred embodiment, the catalyst may contain platinum in an amount of 0.6% to 1.0% by weight, relative to the total weight of the catalyst.

[0071] The sum of the weight percentages of the catalyst components is 100%.

[0072] Another subject of the present invention is a method for preparing the catalyst described above, comprising the following steps: - mixing KL zeolite with at least one silica-type refractory oxide, - a step of shaping the mixture obtained, for example by extrusion, - optional ageing, optional drying or optional calcination of the mixture formed in the previous step, - a step of hydrothermal treatment of the material formed in the previous step in the presence of water vapor; to give a carrier; - an optional calcination step of the support obtained in the previous step, - impregnation of the support with a precursor of a Group VIIIB metal, - drying and calcining the impregnated support to give the catalyst.

[0073] Another subject of the present invention is the use of the catalyst described above in a process for aromatizing a hydrocarbon feedstock containing a C6-C8 paraffin fraction (hydrocarbon chains containing 6 to 8 carbon atoms).

[0074] Another subject of the present invention is a process for aromatizing at least one alkane or cycloalkane contained in a C6-C8 hydrocarbon feedstock, said process being adapted to be operated in the liquid or gas phase, at a temperature between 400°C and 550°C, at a pressure between 2 and 20 MPa, with a molar ratio of hydrogen to hydrocarbon compounds between 1 and 10, and with a weight hourly space velocity (WHSV) between 1 and 10 h -1 with a catalyst, in particular in the form of an oxide, according to any of the variants described, comprising: (a) KL zeolite (structure type LTL); Si / Al molar ratio is between 2.8 and 4, preferably between 2.8 and 3.5, more preferentially 3; (b) refractory oxides of the silica type; (c) Group VIIIB metals.

[0075] Generally, according to the present invention, the method for preparing a catalyst comprises at least the following steps: a) mixing at least one source of KL zeolite (structure type LTL) and at least one source of silica in at least one solvent to obtain a mixture; the mixing is particularly carried out in the form of a mixture of zeolite powder and silica powder and / or a mixture of zeolite powder and silica sol in proportions such that the zeolite content of the final material is at least 70% and / or in the form of a mixture of zeolite powder, silica powder and silica sol in proportions such that the zeolite content of the final material is at least 70%. Any combination of KL zeolite and at least one source of SiO2 silica in the starting mixture may be used so that the proportions of KL zeolite and SiO2 refractory oxide in the catalyst according to the invention are respected. The silica source preferably has a low sodium content, advantageously less than 1000 ppm. b) shaping the mixture resulting from step a); c) optionally ageing the shaped material resulting from step b); d) an optional drying step; e) hydrothermally treating the shaped material (optionally aged in step c) and optionally dried / calcined in step d)) in the presence of water vapor; f) an optional step of calcining the material resulting from step e) to give a calcined support; g) impregnating the support resulting from step e) or f) with a Group VIII metal by contacting it with a solution obtained by dissolving a metal precursor in an aqueous phase; h) drying the impregnated support resulting from step g); i) calcining the dried impregnated support resulting from step h); to provide the catalyst; j) reducing the catalyst obtained as a result of step i); this may be carried out before its use in a catalytic process.

[0076] The preparation method and its various steps are described in detail below.

[0077] (Mixing step a)) According to the present invention, step a) involves mixing at least one source of KL zeolite and at least one source of silica with at least one solvent (e.g., water) to give a mixture that can be shaped.

[0078] The source of silica may be selected from all sources of silica known to those skilled in the art, alone or as a mixture thereof, such as precipitated silica powder, silica gel and colloidal silica sol.

[0079] Preferentially, but without limitation, the one or more precipitated silica powders or silica gels are preferably low in sodium silica (Na<1000 ppm), in particular chosen from the following commercial sources: Nyasil 20 (Nyacol®), Siliaflash P60 (Silicycle®), Siliaflash C60 (Silicycle®), Ultrasil VN3 GR (Evonik®).

[0080] Preferentially, but without limitation, the colloidal silica sol is selected from the following commercial sources: Ludox (WR Grace Davison®), Nyacol (Nyacol Nano Technologies®, Inc. or PQ Corp®), Nalco (Nalco Chemical Company®), Ultra-Sol (RESI Inc®), NexSil (Nyacol Nano Technologies®, Inc. or PQ Corp®).

[0081] The majority of colloidal silica sols are prepared from sodium silicate and therefore necessarily contain sodium. The presence of sodium can prove detrimental to catalytic activity, so an ion exchange step may be necessary to reduce or even eliminate residual sodium. To avoid this step, it is preferable to use low-sodium colloidal silica sols, especially those stabilized with ammonium counterions. These include, for example, Ludox® AS40, stabilized with ammonium counterions, or Nalco 1034A, Ultra-Sol 7H, or NexSil 20A.

[0082] The said silica source or sources used in the process according to the invention are advantageously amorphous synthetic silicas and not natural silicas which may have excessive impurities.

[0083] At least one organic adjuvant may be preferably mixed in during step a).

[0084] The organic adjuvant may be chosen from all additives known to those skilled in the art.

[0085] In the case where at least one organic adjuvant is added in step a), said organic adjuvant may advantageously be chosen, alone or in admixture, from cellulose derivatives, polyethylene glycols, aliphatic monocarboxylic acids, alkylated aromatic compounds, sulfonates, fatty acids, polyvinylpyrrolidones, polyvinyl alcohols, methylcellulose, polyacrylates, polymethacrylates, polyisobutene, polytetrahydrofuran, starch, polysaccharide-type polymers (e.g., xanthan gum), scleroglucans, hydroxyethylcellulose-type derivatives, carboxymethylcellulose (e.g., Methocel®), lignosulfonates and galactomannan derivatives, employed alone or in admixture, the organic adjuvant being preferably carboxymethylcellulose.

[0086] Preferably, the organic adjuvant can be mixed in powder form or in solution in the solvent.

[0087] The solvent may advantageously be chosen from water, physical and chemical solvents, in particular ethanol, alcohols and amines. Preferably, the solvent is water.

[0088] In the context of the present invention, it is entirely possible to consider preparing mixtures of two or more different silica powders and / or different silica sols.

[0089] The order in which the powders of at least the silica source and the KL zeolite source, and optionally at least one organic adjuvant, are mixed with at least one solvent is not important in the case that they are mixed in powder form.

[0090] The mixing of the powder and the solvent can advantageously be carried out all at once.

[0091] The addition of powder and solvent may advantageously be alternating.

[0092] The solvent is added to the powder or to the mixture of powder and sol in such an amount that the mixture can be shaped, for example by extrusion. The amount of solvent introduced may be, in particular, 30% to 40% of the total mass of the oxide mixture (KL zeolite and silica).

[0093] The silica introduced in step a) in the form of precipitated silica or silica gel preferably has a particle size or granulometry of less than 100 μm, highly preferentially less than 80 μm, more preferentially less than 60 μm, even more preferentially less than 20 μm, or even less than 10 μm. The colloidal silica preferably has a particle size or granulometry of between 5 and 200 nm, preferentially between 15 and 50 nm.

[0094] Preferably, said mixing step a) is carried out by batch or continuous kneading.

[0095] In the case where step a) is carried out batchwise, it is advantageously carried out in a kneader, preferably a Z-arm kneader, or a cam mixer, or any other type of mixer, such as a planetary mixer. The mixing step a) makes it possible to obtain a homogeneous mixture of the powder components.

[0096] Preferably, said step a) is carried out by mixing at room temperature for a period of 5 to 60 minutes, preferably 10 to 50 minutes. The rotation speed of the kneader arms is advantageously between 10 and 75 rev / min, preferably between 25 and 50 rev / min.

[0097] Preferably, in the mixing step a) of the process according to the invention, the KL zeolite and silica are introduced in the following proportions: - at least one KL zeolite (with a Si / Al ratio between 2.8 and 4.3, excluding the upper limit): 70% to 90% by weight, highly preferentially 70% to 85% by weight, - 10% to 30% by weight of silica in the form of SiO2 oxide, provided by one or more silica sources.

[0098] This mixture of powders is mixed with the following, relative to the total oxides introduced (KL zeolite and silica): - Solvent: 30% to 40% by weight - at least one organic adjuvant: from 0% to 20% by weight, preferably from 1% to 15% by weight, preferentially from 1% to 10% by weight, very preferentially from 1% to 7% by weight; the addition is carried out to the mixture, - weight percentages are expressed relative to the total weight of the anhydrous material, the sum of the amounts of each of the compounds in the mixture being 100%;

[0099] (Forming process b)) According to the invention, said step b) involves shaping the mixture resulting from step a), which may be carried out by any technique known to those skilled in the art, in particular by extrusion, pelletizing, spheronizing, granulation, etc.

[0100] The mixture resulting from step a) may be shaped, preferably by extrusion.

[0101] If the mixture obtained from step a) is shaped by extrusion, said step b) may advantageously be carried out in a single or twin piston extruder.

[0102] In this case, an organic adjuvant may optionally be added in the mixing step a), the presence of which facilitates shaping by extrusion. The optional organic adjuvant is described above and is introduced in step a) in the proportions indicated above.

[0103] In the case where the preparation method is carried out continuously, the mixing step a) may be coupled with the step b) of forming into shapes by extrusion in the same equipment. According to this embodiment, the extrusion of the mixture, also called "mixed paste", can be carried out either directly at the end of a continuous mixer, for example of the twin-screw type, or by connecting one or more batch mixers to the extruder. The geometry of the die that gives the extrudates their shape can be chosen from dies known to those skilled in the art. They can therefore be, for example, cylindrical, multilobed, grooved or slotted.

[0104] If the mixture obtained from step a) is shaped by extrusion, the amount of solvent added in mixing step a) is adjusted so as to obtain, as a result of this step, whatever the variant used, a mixture or paste that does not flow but is not too dry, and which allows its extrusion under appropriate pressure conditions, well known to those skilled in the art and depending on the extrusion equipment used.

[0105] Preferably, said step b) of shaping by extrusion is carried out at an extrusion pressure of more than 1 MPa, preferably between 3 MPa and 10 MPa.

[0106] After the shaping step, the material obtained, advantageously in the form of extrudates, tablets or beads, has a loss on ignition of between 30% and 40% by weight.

[0107] (Aging process c) (Optional) The process for preparing said material according to the invention may comprise an optional ageing step c) of the shaped material obtained as a result of step b), which, if carried out, is advantageously carried out at a temperature between 0°C and 70°C, preferably between 10°C and 60°C, preferentially between 20°C and 50°C, for a period of 1 minute to 72 hours, preferably between 30 minutes and 72 hours, preferentially between 1 hour and 48 hours, more preferentially between 1 hour and 24 hours.

[0108] Preferably, the ageing step is carried out in air, preferably in humid air with a relative humidity of 20% to 100%, preferably 70% to 100%, which allows good hydration of the material as required to limit the appearance of cracks detrimental to its mechanical strength.

[0109] After this step, the loss on ignition of the shaped and aged material is advantageously between 15% and 25% by weight.

[0110] (Drying process d) (optional) The process for preparing said material according to the invention may comprise a drying step d) of the shaped material obtained as a result of step b) or, if step c) is carried out, as a result of step c), which, if carried out, is advantageously carried out at a temperature of 0 to 200°C, preferably 50 to 150°C, preferentially 70 to 150°C, for a period of 1 minute to 72 hours, preferably 30 minutes to 72 hours, preferentially 1 hour to 48 hours, more preferentially 1 hour to 24 hours.

[0111] The loss on ignition of the dried material obtained in this step is advantageously between 7% and 10% by weight.

[0112] (Optional baking step d') Advantageously, the shaped material obtained from the ageing step c) or from the drying step d) may optionally undergo a calcination step d') at a temperature between 200 and 600° C., preferably between 250 and 450° C., for a period of 1 to 12 hours, preferably between 1 and 4 hours. This calcination step is particularly useful for eliminating organic adjuvants used to facilitate the shaping of the material.

[0113] The optional calcination step d') is advantageously carried out in a gas stream containing oxygen; for example, the extrudates are preferably calcined with dry air or air of various degrees of humidity, or heat-treated in the presence of a gas mixture containing an inert gas, preferably nitrogen and oxygen. The gas mixture used preferably contains at least 5% by volume, or more preferably at least 10% by volume, of oxygen. The calcination step d') may include a gradual temperature increase and, optionally, a temperature plateau at a temperature between 100 and 200°C.

[0114] (Hydrothermal treatment step e) The preparation process according to the invention comprises a step e) of hydrothermal treatment in the presence of water vapor of the material obtained from step b), c), d) or d').

[0115] The material shaped in step b), optionally time-aged in step c) and optionally dried / calcined in step d) is subjected to a hydrothermal treatment in the presence of water vapor at a temperature of 200-550°C.

[0116] The hydrothermal treatment can be carried out by any technique known to those skilled in the art. The term "hydrothermal treatment" refers to placing the mixed carrier in contact with water in the vapor or liquid phase at any stage in the production. The term "hydrothermal treatment" can refer in particular to steam treatment, i.e., steaming, autoclaving, calcination in moist air, or rehydration. Without any reduction in the scope of the present invention, the effect of such treatment is, in particular, to make the silica component mobile.

[0117] In one embodiment, the hydrothermal treatment step e) may be carried out at atmospheric pressure, at a temperature between 200°C and 550°C, more preferentially for a period between 30 minutes and 5 hours. According to the invention, the hydrothermal treatment is a treatment containing water vapor and a gas at a temperature. The gas is advantageously air or nitrogen. The volume composition of water in the gas may be between 20% and 100%, preferably between 30% and 90%, and highly preferentially between 40% and 70%.

[0118] The loss on ignition of the support obtained after this step is advantageously between 15% and 20% by weight.

[0119] In one preferred embodiment, the hydrothermal treatment step e) may wholly or partly replace the calcination step d') or f).

[0120] (Optional baking step f)) Advantageously, the shaped material obtained from the hydrothermal treatment step e) may optionally undergo one or more sequences of calcination steps f) at temperatures between 200 and 680° C., preferably between 400 and 660° C., for a period of 1 to 12 hours, preferably 1 to 4 hours. This calcination step may be particularly useful for freeing the microporosity of the zeolite from residual chemisorbed water.

[0121] Said optional calcination step f) is advantageously carried out in a gas stream containing oxygen; for example, the extrudates are preferably calcined in dry air or air with various degrees of humidity, or heat-treated in the presence of a gas mixture containing an inert gas, preferably nitrogen and oxygen. The gas mixture used preferably contains at least 5% by volume, and indeed more preferably at least 10% by volume, of oxygen.

[0122] The loss on ignition of the extrudates obtained after this step is advantageously between 1% and 10% by weight.

[0123] As a result of steps a) to e) or a) to f) of the preparation process according to the invention, the material obtained, hereinafter referred to as "carrier", is in the form of an extrudate or pellets or tablets or beads.

[0124] However, it is not excluded that the materials obtained are then introduced into equipment that makes it possible, for example, to round their surface, such as a pan or any other equipment that makes it possible to spheronize the materials.

[0125] The catalyst carrier according to the present invention is made of a composite KL zeolite-SiO2 material and has a thickness of 80-200 m 2 / g specific surface area.

[0126] The total pore volume of the catalyst support according to the present invention is 0.35 to 0.6 cm 3 / g.

[0127] The macropore volume of the catalyst support according to the present invention is 0.08 to 0.16 cm 3 / g.

[0128] The mesopore volume of the catalyst support according to the present invention is 0.2 cm 3 / g~0.4cm 3 / g.

[0129] The micropore volume of the catalyst support according to the present invention is less than 0.07 cm 3 / g and preferably less than 0.03 cm 3 / g or more.

[0130] The sodium content of the catalyst support according to the invention is less than 0.2% by weight.

[0131] The catalyst support according to the invention exhibits entirely satisfactory mechanical properties, in particular with regard to mechanical strength.

[0132] In particular, the mechanical strength of the catalyst support according to the invention, measured by the single pellet crushing test, hereinafter referred to as SPC, is at least 0.5 daN / mm, preferably at least 0.6 daN / mm and preferentially at least 0.7 daN / mm.

[0133] The increase in mechanical strength makes it possible to contemplate using said catalyst support in relatively high temperature processes in the presence of water or solvents.

[0134] Steps g), h) and i) make it possible to obtain the catalyst according to the invention from the support obtained in step e) or f).

[0135] (Step g): Impregnation step) The catalyst support according to the invention is impregnated by the addition of a metal of group VIII, preferentially of the Pt type, precious metal, by contacting the support with an impregnation solution of a precursor of the metal.

[0136] The platinum precursor used is preferentially chosen from the following precursors, in a non-limiting list: hexachloroplatinic acid (HPtCl), bromoplatinic acid, ammonium chloroplatinate, platinum chloride, dichlorocarbonylplatinum dichloride, tetraamineplatinum chloride (Pt(NH)Cl), tetraamineplatinum nitrate Pt(NH)(NO) or dihydroxydiamineplatinum. Organoplatinum complexes, such as platinum(II) diacetylacetonate, may also be used.

[0137] The precursor is diluted in an aqueous phase to form the impregnation solution.

[0138] The metals may be introduced onto the support by various techniques known to those skilled in the art, such as dry impregnation, excess impregnation, impregnation in a fluidized bed, impregnation by pore filling, etc., preferably by dry impregnation or excess impregnation, which is carried out to provide good distribution and dispersion of the metal phase.

[0139] The amount of Group VIII metal introduced in step g) of the preparation process according to the invention is preferably as follows: A metal, preferably platinum; as a mass percentage measured relative to the total mass of the final catalyst, between 0.1% and 10% by weight, preferably between 0.2% and 5% by weight, preferentially between 0.3% and 2% by weight, very preferentially between 0.5% and 1.2% by weight, and even more preferentially between 0.6% and 1.0% by weight.

[0140] (drying process h)) In step g), the material thus obtained undergoes a drying step to remove residual water from the porosity, which may be carried out in a traversing bed, a swept bed, a static system, etc. The temperature used in this step is preferably between 50°C and 200°C, preferentially between 60°C and 150°C, and very preferentially between 80°C and 120°C.

[0141] (Firing process i) In step h), the material thus obtained undergoes a calcination step necessary for the decomposition of the metal precursors and for the effective distribution and dispersion of the metal phase. This step is carried out in a gas stream, either air or air diluted with a neutral gas (N, Ar, etc.). This step may preferably be carried out in a stream of pure air. The temperature used in this step may preferably be between 200°C and 500°C, preferentially between 250°C and 450°C, and very preferentially between 350°C and 420°C. Step i) may include a gradual temperature increase and, optionally, a plateau at a temperature between 100 and 200°C.

[0142] (Catalyst reduction step j) In step i), the material thus obtained may undergo a reduction step necessary to activate the metal precursor. This step is preferably carried out in a gas stream of either pure hydrogen or hydrogen diluted with a neutral gas (N, Ar, etc.), either pre-charged or in situ, before contacting with the feedstock. The temperature used in this step is preferably between 300°C and 550°C, preferentially between 350°C and 500°C, and very preferentially between 450°C and 500°C.

[0143] As a result of step i) or j), the specific surface area of ​​the catalyst according to the present invention is 80 to 200 m 2 / g and the micropore volume is 0.04 cm 3 / g or less, more specifically 0.015 to 0.04 cm 3 / g.

[0144] As a result of the preparation method according to the invention, the Cl content of the catalyst is advantageously less than 0.5% and the Na content is less than 0.2%, without any need to use washing operations.

[0145] The metal content, preferably the platinum content, of the catalyst according to the invention is between 0.1% and 10% by weight, preferably between 0.2% and 5% by weight, very preferentially between 0.3% and 2% by weight, more preferentially between 0.5% and 1.2% by weight and very advantageously between 0.6% and 1.0% by weight, based on the weight of the anhydrous catalyst.

[0146] The catalyst according to the present invention has a metal dispersion rate, particularly a platinum dispersion rate, of 50% to 70%.

[0147] The catalyst obtained after application of the Group VIII metal, preferably platinum, by impregnation onto the support is contacted with a gaseous feedstock for processing in a reactor, which may be either a fixed bed reactor or a radial reactor.

[0148] The catalyst obtained as a result of the preparation process according to the invention may be used in catalysis, in particular in the aromatization of C6 / C8 paraffin fractions.

[0149] This type of catalyst has been shown to exhibit improved activity and aromatics yields, especially for the aromatization of the C6-C8, especially C6-C7, fraction, compared to catalysts known to those skilled in the art. The process for preparing the catalyst according to the invention further has the advantage of reducing the environmental impact of the preparation of the catalyst, due to the fact that no halides are used and additional washing steps are omitted.

[0150] The present invention is illustrated by the following examples, which are not intended to be limiting in any way.

[0151] (Example) Example 1: Preparation of Catalyst A Pt / KL-SiO2 (Comparative Example) Support A is prepared by mixing together KL zeolite powder (Tosoh; Si / Al=3) (70%), precipitated silica (Nyasil20) (30%) and Methocel (K15M) (3% relative to the total mass of the oxides) in a Brabender mixer. Water is added dropwise until a paste is obtained, and mixing is continued for 20 minutes. The paste obtained is then extruded in an MTS piston extruder using a cylindrical die with a diameter of 1.6 mm. The extrudates are aged in a ventilated oven at 80°C for 16 hours and then calcined at 550°C for 4 hours.

[0152] Catalyst A is obtained in excess by fluidized-bed impregnation of this support. To achieve this, 25 g of the support is first calcined in air at 520 °C for 2 hours, and then deactivated with water by adding water dropwise to the support as it rotates in the pan. The precursors of Pt(NH3)4Cl2 and KNO3 are dissolved. The deactivated support is placed in a fluidized bed for fluidized-bed impregnation. Fluidization is maintained at a rate of 25 mL / min for 24 hours.

[0153] After fluidization, the solution is removed. The catalyst is then washed four times with 200 mL of water in a fluidized bed at a rate of 25 mL / min for 30 minutes. The catalyst is dried in an oven at 120°C for 12 hours, first held at 150°C for 1 hour, and then calcined as follows: 250°C for 1 hour and 400°C for 2 hours.

[0154] Table 1 below details the formulation and characteristics of Catalyst A.

[0155] [Table 1]

[0156] Example 2: Preparation of Catalyst B Pt / KL-SiO2 (Comparative Example) Carrier B is prepared by mixing together KL zeolite powder (Tosoh; Si / Al=3) (70%), precipitated silica (Siliaflash P60 40-63 μm; Silicycle) (10%), a source of colloidal silica sol (20%), and Methocel (K15M) (3% relative to the total mass of the oxides) in a Brabender mixer. Water is added dropwise until a paste is obtained, and mixing is continued for 20 minutes. The paste obtained is then extruded in an MTS piston extruder using a cylindrical die with a diameter of 1.6 mm. The extrudates are aged in a ventilated oven at 80 ° C for 16 hours and then calcined at 550 ° C for 4 hours.

[0157] Catalyst B is obtained in excess by fluidized-bed impregnation of this support. To achieve this, 25 g of the support is pre-calcined in air at 520 °C for 2 hours, then deactivated with water by adding water dropwise to the support as it rotates in the pan. The precursors of Pt(NH3)4Cl2 and KNO3 are dissolved. The deactivated support is placed in a fluidized bed for fluidized-bed impregnation. Fluidization is maintained at a rate of 25 mL / min for 24 hours.

[0158] After fluidization, the solution is removed. The catalyst is then washed in the fluidized bed with 200 mL of water four times for 30 minutes at a rate of 25 mL / min. The catalyst is dried in an oven at 120°C for 12 hours, first held at 150°C for 1 hour, and calcined at 250°C for 1 hour and 400°C for 2 hours.

[0159] Table 2 below details the formulation and characteristics of Catalyst B.

[0160] [Table 2]

[0161] Example 3: Preparation of Catalyst C Pt / KL-SiO2 (Comparative Example) Support C is prepared by mixing KL zeolite powder (Tosoh; Si / Al=3) (70%), precipitated silica (Siliaflash P60 40-63 μm; Silicycle) (10%), a source of colloidal silica sol (20%), and Methocel (K15M) (3% relative to the total mass of the oxides) together in a Brabender mixer. Water is added dropwise until a paste is obtained, and mixing is continued for 20 minutes. The resulting paste is then extruded in an MTS piston extruder using a cylindrical die with a diameter of 1.6 mm. The extrudates are aged for 16 hours at 80 °C in a ventilated oven and then hydrothermally treated for 3 hours at 600 °C in a gas stream containing 50% by volume of water in air. The extrudates are then calcined for 2 hours at 550 °C.

[0162] Catalyst C is obtained in excess by fluidized-bed impregnation of this support. To achieve this, 25 g of the support is pre-calcined in air at 520 °C for 2 hours, then deactivated with water by adding water dropwise to the support as it rotates in the pan. The precursors of Pt(NH3)4Cl2 and KNO3 are dissolved. The deactivated support is placed in a fluidized bed for fluidized-bed impregnation. Fluidization is maintained at a rate of 25 mL / min for 24 hours.

[0163] After fluidization, the solution is removed. The catalyst is then washed in the fluidized bed with 200 mL of water four times for 30 minutes at a rate of 25 mL / min. The catalyst is dried in an oven at 120°C for 12 hours, held at 150°C for 1 hour, and then calcined at 250°C for 1 hour and 400°C for 2 hours.

[0164] Table 3 below details the formulation and characteristics of Catalyst C.

[0165] [Table 3]

[0166] Example 4: Preparation of Catalyst D Pt / KL-SiO2 (according to the present invention) Support D is prepared by mixing KL zeolite powder (Tosoh; Si / Al=3) (70%), precipitated silica (Siliaflash C60 (5-20 μm; Silicycle) (30%), and Methocel (K15M) (3% relative to the total mass of the oxides) together in a Brabender mixer. Water is added dropwise until a paste is obtained, and mixing is continued for 20 minutes. The paste obtained is then extruded in an MTS piston extruder using a cylindrical die with a diameter of 1.6 mm. The extrudates are aged for 16 hours at 80°C in a ventilated oven, calcined for 2 hours at 550°C, and then hydrothermally treated for 3 hours at 500°C in a gas stream containing 50% by volume of water in air. The extrudates are then calcined for 2 hours at 550°C.

[0167] Catalyst D is obtained by dry impregnation of support D with a solution of Pt(NH3)4Cl2. To achieve this, 50 g of support is pre-calcined in air at 520 °C for 2 hours and then saturated with water in a closed container under a humid atmosphere. The Pt(NH3)4Cl2 precursor is dissolved in an aqueous solution. The Pt solution is added dropwise to the support as it rotates in a pan for 15 minutes. The catalyst is stored in a closed container for 24 hours, then dried in an oven at 120 °C for 12 hours and calcined at 400 °C.

[0168] [Table 4]

[0169] Example 5: Preparation of Catalyst E Pt / KL-SiO2 (According to the Invention) Carrier E is prepared by mixing together KL zeolite powder (Tosoh; Si / Al=3) (70%), precipitated silica (Siliaflash C60 40-63 μm; Silicycle) (5%), a source of colloidal silica sol (25%), and Methocel (K15M) (3% relative to the total mass of the oxides) in a Brabender mixer. Water is added dropwise until a paste is obtained, and mixing is continued for 20 minutes. The paste obtained is then extruded in an MTS piston extruder using a cylindrical die with a diameter of 1.6 mm. The extrudates are aged in a ventilated oven at 80 ° C for 16 hours, dried at 120 ° C for 12 hours, calcined at 550 ° C for 2 hours, and then hydrothermally treated at 500 ° C for 3 hours in a gas stream containing 50% by volume of water in air. The extrudates are then calcined at 550 ° C for 2 hours.

[0170] Catalyst E is obtained by dry impregnation of support E with a solution of Pt(NH3)4Cl2. To achieve this, 50 g of support is pre-calcined in air at 520 °C for 2 hours and then saturated with water in a closed container under a humid atmosphere. The Pt(NH3)4Cl2 precursor is dissolved in an aqueous solution. The Pt solution is added dropwise to the support as it rotates in a pan for 15 minutes. The catalyst is stored in a closed container for 24 hours, then dried in an oven at 120 °C for 12 hours and calcined at 400 °C.

[0171] [Table 5]

[0172] (Example 6: Preparation of catalyst F Pt / KL-SiO2 (comparative example)) Support F is prepared by mixing together KL zeolite powder (Tosoh; Si / Al=3) (70%), precipitated silica (Siliaflash P60 40-63 μm; Silicycle) (30%), and Methocel (K15M) (3% relative to the total mass of the oxides) in a Brabender mixer. Water is added dropwise until a paste is obtained, and mixing is continued for 20 minutes. The paste obtained is then extruded in an MTS piston extruder using a cylindrical die with a diameter of 1.6 mm. The extrudates are aged in a ventilated oven at 80° C. for 16 hours and then calcined at 550° C. for 4 hours.

[0173] Catalyst F is obtained by dry impregnation of support F with a solution of Pt(NH3)4Cl2. To achieve this, 50 g of support is pre-calcined in air at 520 °C for 2 hours and then saturated with water in a closed container under a humid atmosphere. The Pt(NH3)4Cl2 precursor is dissolved in an aqueous solution. The Pt solution is added dropwise to the support as it rotates in a pan for 15 minutes. The catalyst is stored in a closed container for 24 hours, then dried in an oven at 120 °C for 12 hours and calcined at 400 °C.

[0174] Table 6 below details the formulation and characteristics of Catalyst F.

[0175] [Table 6]

[0176] Example 7: Preparation of Catalyst G Pt / KL-SiO2 (Comparative Example) Support G is prepared by mixing together KL zeolite powder (Tosoh; Si / Al=3) (70%), precipitated silica (Siliaflash P60 40-63 μm; Silicycle) (30%), and Methocel (K15M) (3% relative to the total mass of the oxides) in a Brabender mixer. Water is added dropwise until a paste is obtained, and mixing is continued for 20 minutes. The paste obtained is then extruded in an MTS piston extruder using a cylindrical die with a diameter of 1.6 mm. The extrudates are aged for 16 hours at 80°C in a ventilated oven and then hydrothermally treated for 3 hours at 600°C in a gas stream containing 50% by volume of water in air. The extrudates are then calcined at 550°C for 2 hours.

[0177] Catalyst G is obtained by dry impregnation of support F with a solution of Pt(NH3)4Cl2. To achieve this, 50 g of support is pre-calcined in air at 520 °C for 2 hours and then saturated with water in a closed container under a humid atmosphere. The Pt(NH3)4Cl2 precursor is dissolved in an aqueous solution. The Pt solution is added dropwise to the support as it rotates in a pan for 15 minutes. The catalyst is stored in a closed container for 24 hours, then dried in an oven at 120 °C for 12 hours and calcined at 400 °C.

[0178] Table 7 below details the formulation and characteristics of Catalyst G.

[0179] [Table 7]

[0180] Example 8: Aromatization of the C6 / C7 Fraction Approximately 1 g of the prepared catalysts A to G is loaded into a fixed-bed reactor. Once loaded, the catalysts are dried in a nitrogen stream at 150°C and then reduced under a H stream at 470°C for 12 hours. The temperature is then reduced to 400°C and the feedstock is injected.

[0181] The tests are carried out at 4 bar with a temperature sweep from 430 to 500 °C, with a H2 / hydrocarbon molar ratio of 4. The feed composition is shown in Table 8. The mass flow rate is 1 g of feed (g catalyst) -1 h -1 is.

[0182] [Table 8]

[0183] Table 9 below summarizes the catalytic performance results of Examples 1 to 7 corresponding to Catalysts A to G.

[0184] The feed conversion is defined as follows:

[0185] Flow rates are expressed in g / h and concentrations in wt%.

[0186] Conversion rate i&nP6-P7=(1-(output flow rate × (n-P6(wt%) + iso-P6(wt%) + n-P7(wt%) + iso-P7(wt%)) output) / (input flow rate × (n-P6(wt%) + iso-P6(wt%) + n-P7(wt%) + iso-P7(wt%)) input)) × 100 P6 and P7 represent n-paraffins or isoparaffins with 6 and 7 carbon atoms, respectively.

[0187] The aromatic yield is defined as follows: Aromatic compound yield = output flow rate × (A6 (wt%) + A7 (wt%) + A8 (wt%)) / (input flow rate) A6, A7 and A8 represent aromatic compounds having 6, 7 and 8 carbon atoms, respectively.

[0188] These conversions and yields are measured at 480° C. with WHSV=1.

[0189] [Table 9]

[0190] The conversion rate of the comparative catalysts was at most 83.3% of that of Catalyst A, and the yield of aromatic compounds was at most 75.6% of that of Catalyst B.

[0191] Catalysts D and E according to the invention have much higher conversions of more than 86% or even more than 88% and aromatic yields of more than 80%. The above examples 1 to 8 particularly show that all steps of the process according to the invention, in particular the presence of the step of hydrothermal treatment of the support under the required conditions, are essential to improve the performance and achieve a P6P7 conversion of more than 86% and an aromatic yield of more than 80%.

Claims

1. Minimum 70% by weight of KL zeolite, SiO ２ 1. A method for preparing an aromatization catalyst comprising a silica-type refractory oxide and a Group VIIIB metal, the method comprising at least the following steps: a) at least one source of KL zeolite of structural type LTL and SiO ２ mixing at least one source of silica with at least one solvent selected from water, physical solvents and chemical solvents, optionally in the presence of an organic adjuvant; providing a mixture; b) shaping the mixture obtained as a result of step a), preferably by extrusion; c) an optional step of ageing of said shaped material in air, preferably in moist air having a relative humidity of 20% to 100%, for a period of 1 minute to 72 hours at a temperature of 0 to 70°C; d) an optional step of drying the shaped and optionally aged material at a temperature of 0 to 200°C for a period of 1 minute to 72 hours; optionally followed by a step d') of calcination at a temperature of 200 to 600°C, preferably 250 to 450°C, for a period of 1 to 12 hours, preferably 1 to 4 hours; e) hydrothermally treating the shaped, optionally aged and optionally dried / calcined material of step b) in the presence of water vapor at a temperature of 200-550°C, preferably at atmospheric pressure, for a period of 30 minutes to 5 hours; to give a catalyst support; f) an optional step of calcining the support resulting from step e) at a temperature of 200 to 680°C, preferably 400 to 660°C, for a period of 1 to 12 hours, preferably 1 to 4 hours; to provide a calcined catalyst support; g) impregnation with a group VIII metal, preferably platinum, by contacting the support resulting from step e) or f) with a solution of a precursor of said metal dissolved in an aqueous phase; the metal content on the catalyst is between 0.1% and 10% by weight, preferably between 0.2% and 5% by weight, preferentially between 0.3% and 2% by weight, and very preferentially between 0.5% and 1.2% by weight, relative to the total mass of the anhydrous catalyst; h) drying the impregnated material resulting from step g), preferably at a temperature between 50°C and 200°C; i) calcining the dried material resulting from step h) in a gas stream of either pure air or air diluted with a neutral gas at temperatures between 200°C and 500°C, preferentially between 250°C and 450°C, very preferentially between 350°C and 420°C; to give a calcined catalyst.

2. 10. The method of claim 1, comprising the steps of: j) reducing the calcined catalyst resulting from step i), before contacting it with the feedstock, by contacting the catalyst with a gas stream containing hydrogen, either pure or diluted with a neutral gas, at a temperature between 300°C and 550°C, preferentially between 350°C and 500°C, and very preferentially between 450°C and 500°C.

3. 3. A process according to claim 1 or 2, wherein step a) is carried out by mixing at room temperature for a period of 5 to 60 minutes, preferably 10 to 50 minutes.

4. KL zeolite and SiO ２ Silica is prepared in step a) as a mixture of oxides in the following proportions: - at least one KL zeolite: from 70% to 90% by weight, preferably from 70% to 85% by weight, and at least one SiO ２ Source of silica: 10% to 30% by weight, preferably 15% to 30% by weight Introduced in The mixture may be: solvent: from 10% to 30% by weight relative to the total weight of said mixture of oxides, and at least one organic adjuvant: from 0% to 20% by weight, preferably from 1% to 15% by weight, preferentially from 1% to 10% by weight and very preferentially from 1% to 7% by weight, relative to the total weight of said mixture of oxides; Mixed with The sum of the amounts of each compound introduced in this step is 100%.

5. 5. A process according to any one of claims 1 to 4, wherein a single source of silica is used in step a), which single source of silica is preferably precipitated silica or silica gel, very preferentially precipitated silica.

6. 5. The process according to claim 1, wherein two different sources of silica are used in step a).

7. 7. The method of claim 6, wherein the two sources of silica are precipitated silica and colloidal silica sol.

8. 8. A process according to any one of claims 5 to 7, wherein the particle size or granulometry of the silica used in step a) is less than 100 μm, preferentially less than 80 μm, more preferentially less than 60 μm, even more preferentially less than 20 μm or indeed less than 10 μm for precipitated silicas or silica gels, and a particle size between 5 and 200 nm, preferentially between 15 and 50 nm for colloidal silica sols.

9. 9. The method according to any one of claims 1 to 8, wherein the organic adjuvant is chosen from cellulose derivatives, polyethylene glycol, aliphatic monocarboxylic acids, alkyl aromatic compounds, sulfonates, fatty acids, polyvinylpyrrolidone, polyvinyl alcohol, methylcellulose, polyacrylates, polymethacrylates, polyisobutene, polytetrahydrofuran, starch, polysaccharide type polymers, scleroglucan, hydroxyethylcellulose type derivatives, carboxymethylcellulose, lignosulfonates and galactomannan derivatives, used alone or in mixtures, preferably carbomethylcellulose.

10. The specific surface area of ​​the support obtained as a result of step e) or f) is between 80 and 200 m ２ / g, and the total pore volume is 0.35 to 0.6 cm ３ / g, and the macropore volume is 0.08 to 0.16 cm ３ / g, and the mesopore volume is 0.2 cm ３ / g to 0.4 cm ３ / g and the micropore volume is 0.07 cm ３ / g, the sodium content is less than 0.2% by weight, and the mechanical strength, measured by the single pellet crushing test, hereinafter referred to as SPC, is at least 0.5 daN / mm or more, preferably at least 0.6 daN / mm or more and preferentially at least 0.7 daN / mm or more.

11. KL Zeolite-SiO containing at least 70% KL Zeolite ２ An aromatization catalyst support in the form of a composite material, obtained in step e) or f) of the process according to any one of claims 1 to 10, having a specific surface area of ​​80 to 200 m ２ / g, and the total pore volume is 0.35 to 0.6 cm ３ / g, and the macropore volume is 0.08 to 0.16 cm ３ / g, and the mesopore volume is 0.2 cm ３ / g to 0.4 cm ３ / g and the micropore volume is 0.07 cm ３ / g, the sodium content is less than 0.2% by weight, and the mechanical strength, measured by the single pellet crushing test, hereinafter referred to as SPC, is at least 0.5 daN / mm or more, preferably at least 0.6 daN / mm or more and preferentially at least 0.7 daN / mm or more.

12. Catalyst for the aromatization of C6-C8 paraffin fractions, which can be prepared as claimed in any one of claims 1 to 10, comprising at least 70% by weight of KL zeolite of LTL structural type, having a Si / Al ratio between 2.8 and 4, preferably between 2.8 and 3.5, 10% by weight to 30% by weight of SiO ２ The catalyst comprises a silica-type refractory oxide, a Group VIIIB metal, preferably platinum, and has a specific surface area of ​​80 to 200 m ２ / g and the micropore volume is 0.04 cm ３ / g, the content of metal of group VIIIB is between 0.1% and 10% by weight, preferably between 0.2% and 5% by weight, very preferentially between 0.3% and 2% by weight, even more preferentially between 0.5% and 1.2% by weight, and the dispersion of said metal is between 50% and 70%.

13. 13. The aromatization catalyst of claim 12, wherein the metal is platinum and the platinum content is between 0.6% and 1.0% by weight relative to the total weight of the catalyst.

14. 14. The aromatization catalyst according to claim 12 or 13, wherein the KL zeolite content is between 70% and 85% by weight, the refractory oxide content is between 15% and 30% by weight, and the sum of all constituents of the catalyst, including metals, is 100%.

15. A process for aromatizing at least one alkane or cycloalkane contained in a hydrocarbon feedstock containing a C6-C8 paraffin fraction, which process is carried out by contacting a catalyst prepared as claimed in any one of claims 1 to 10 or a catalyst as claimed in any one of claims 12 to 14 with a gaseous feedstock for treatment in the presence of hydrogen, operating in the liquid or gas phase, at a temperature of 400°C to 550°C, at a pressure of 2 to 20 MPa, with a molar ratio of hydrogen to hydrocarbon compounds of 1 to 10, and with a weight hourly space velocity (WHSV) of 1 to 10 h －１ How to be.

16. 16. The aromatization process of claim 15, wherein the conversion of n-paraffins and isoparaffins to C6-C7 is 85% or more and the aromatics yield is 80% or more.

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