Process for the dehydrogenation of paraffins and / or naphthenes in the presence of a catalyst based on a support containing a high density of macropores

Abstract

A process for dehydrogenating a hydrocarbon feed comprising paraffins and / or naphthenes, in which said feed is contacted with a catalyst comprising an active phase based on at least one metal from group VIII, at least one element M1 selected from tin, germanium, lead, gallium, indium and thallium, and at least one element M2 selected from the alkali or alkaline earth elements, and a support comprising at least one refractory oxide, characterized in that the average macropore density of said support is greater than or equal to 2000 kpores / mm² and less than 5000 kpores / mm² and in that the value of the packed filling density (DRT) is between 0.50 g / mL and 0.68 g / ml.

Description

Title of the invention: Process for the dehydrogenation of paraffins and / or naphthenes in the presence of a catalyst based on a support containing a high density of macropores. Field of the invention

[0001] The present invention relates to the field of hydrocarbon compound conversion, more specifically to the dehydrogenation of a hydrocarbon feedstock comprising paraffinic and / or naphthenic compounds, and more particularly to the dehydrogenation of propane in the presence of a catalyst to produce olefins, and more particularly propylene. Prior art

[0002] Paraffin and / or naphthene dehydrogenation processes are promising avenues for the dedicated production of unsaturated compounds, particularly olefins, for which global demand is growing. Indeed, among the possible olefin production methods, such as thermal or catalytic cracking, metathesis, and alcohol dehydration, paraffin and / or naphthene dehydrogenation processes offer higher yields and are highly selective. Propylene production, in particular, is especially attractive given the increasing demand for polypropylene and propylene derivatives such as acrylic acid and acrylonitrile. The need for catalyst and process optimization therefore remains a constant.

[0003] The dehydrogenation reactions of paraffins and / or naphthenes are highly endothermic and reversible. Conversion rates are limited by thermodynamic equilibrium conditions. In the case of propane dehydrogenation (AH = -125 kJ / mol), a high temperature above 600°C is conventionally used, and the equilibrium conversion under these conditions is on the order of 30% under industrial conditions. Since separating olefin from paraffin is a costly step in terms of investment and energy, it is essential to work towards maximum feed conversion to maximize process productivity.

[0004] The severe conditions enabling this are thus highly favorable to the secondary reactions of deep dehydrogenation, olefin oligomerization, hydrogenolysis, cracking, and coke formation. These byproducts and this coke formation lead to the deactivation of the dehydrogenation catalysts and necessitate the regeneration of the catalyst, and in particular of the metallic phase, by at least one combustion step. The challenge, therefore, is to achieve to develop an active but also selective and stable catalyst for an economically viable process.

[0005] Among the catalysts suitable for the dehydrogenation of paraffins and more particularly for the dehydrogenation carried out in a moving bed process known as CCR (“Continuons Catalytic Reforming” according to the Anglo-Saxon terminology), we can notably mention platinum (Pt) based catalysts and more particularly PtSnK type catalysts.

[0006] Numerous prior art works describe this type of dehydrogenation catalyst and the means implemented to improve its activity, selectivity, and stability. In particular, some patents recommend increasing the average diameter of the mesopores and / or introducing macropores.

[0007] To adapt the catalyst for propane dehydrogenation, US patent 4,914,075 states that it is essential to perform high-temperature calcination, i.e., between 1000°C and 1200°C, of ​​the tin-containing alumina support in order to increase the average pore diameter of said support and thus promote the diffusion of heavy species and limit deactivation. This results in a decrease in the specific surface area of ​​the support, an increase in density, and a change in the crystalline phase of the alumina from gamma to predominantly theta (> 75% by weight relative to the total weight of the alumina).

[0008] US patent 8,993,474 discloses a catalyst in which the tin-containing alumina support is obtained by a calcination step carried out for 6 hours at 1050°C, resulting in a support with a theta crystallinity greater than 90% by weight relative to the total weight of the alumina and exhibiting average mesopore and macropore diameters of between 5 and 100 nm and between 0.1 and 20 pm, respectively. This type of catalyst exhibits improved performance compared to those whose supports have not undergone a high-temperature calcination step.

[0009] The Applicant, in its research to improve the performance of heterogeneous catalysts for the dehydrogenation of paraffins and / or naphthenes, has surprisingly identified that the performance of the catalysts, in terms of activity, selectivity and stability, is increased by selecting a catalyst comprising a specific support having a compromise between its macropore density and its packed filling density (DRT) value. Objects of the invention

[0010] The present invention relates to a process for dehydrogenating a hydrocarbon feed comprising paraffins and / or naphthenes, in which said feed is contacted with a catalyst at a pressure between 0.1 MPa and 4 MPa, at a temperature between 200°C and 800°C, and with a spatial velocity liquid volume between 0.5 h1 and 50 h1, said catalyst comprising an active phase based on at least one metal of group VIII, at least one element M1 selected from tin, germanium, lead, gallium, indium and thallium, and at least one element M2 selected from the alkali or alkaline earth elements, and a support comprising at least one refractory oxide, characterized in that the average macropore density of said support is greater than or equal to 2000 kpores / mm2 (kilo pores / mm2) and less than 5000 kpores / mm2 (kilo pores / mm2) and in that its packed filling density (PTD) value is between 0.50 g / mL and 0.68 g / mL.

[0011] It has been shown surprisingly that the use of a catalyst comprising a macroporous texture support having a specific macropore density associated with a well-determined packed filling density (DRT) makes it possible to obtain, by synergy effect, an activity, selectivity and stability in the dehydrogenation of a hydrocarbon feed comprising paraffinic and / or naphthenic compounds which are superior to those obtained by using catalysts not simultaneously exhibiting all of these combinations of characteristics.

[0012] According to one or more embodiments, the support is an alumina.

[0013] According to one or more embodiments, the specific surface area of ​​the support is between 170 m2 / g and 250 m2 / g.

[0014] According to one or more embodiments, the average macroporous diameter of said support is between 0.10 pm and 0.80 pm.

[0015] According to one or more embodiments, the specific surface area of ​​said support is between 190 m2 / g and 220 m2 / g.

[0016] According to one or more embodiments, the packed filling density (DRT) value of said support is between 0.55 g / mL and 0.65 g / mL.

[0017] According to one or more embodiments, the content of group VIII metal is between 0.02% and 2% by elemental weight of group VIII metal relative to the total weight of the catalyst.

[0018] According to one or more embodiments, the metal of group VIII is platinum.

[0019] According to one or more embodiments, the content of element Ml is included between 0.01% and 10% by elemental weight in Ml element relative to the total weight of the catalyst.

[0020] According to one or more embodiments, the element Ml is tin.

[0021] According to one or more embodiments, the surface density of M2 elements is between 0.5 atoms and 2 atoms of element M2 / nm2.

[0022] According to one or more embodiments, the element M2 chosen from among the alkali or alkaline-earth elements is potassium.

[0023] According to one or more embodiments, the potassium content, expressed as an element, is between 0.5% and 3% by weight relative to the total weight of the catalyst.

[0024] According to one or more embodiments, the hydrocarbon filler comprises paraffinic and / or naphthenic compounds containing from 2 to 30 carbon atoms per molecule, taken alone or in mixture.

[0025] According to one or more embodiments, the hydrocarbon filler comprises paraffinic compounds having 2 to 5 carbon atoms per molecule and / or nathenic compounds having 5 to 12 carbon atoms. List of figures

[0026] Fig. 1 is a photograph of the Al support according to example 1 taken by Scanning Electron Microscopy (SEM) on a polished section with a magnification of x2500 and a resolution of 2048x1536 pixels.

[0027] Fig. 2 is a photograph of support B1 according to example 1 taken by Scanning Electron Microscopy (SEM) on polished section with a magnification of x2500 and a resolution of 2048x1536 pixels.

[0028] Fig. 3 is a photograph of the support Cl according to example 1 taken by Scanning Electron Microscopy (SEM) on a polished section with a magnification of x2500 and a resolution of 2048x1536 pixels.

[0029] Fig. 4 is a photograph of the DI support according to example 1 taken by Scanning Electron Microscopy (SEM) on a polished section with a magnification of x2500 and a resolution of 2048x1536 pixels. Detailed description of the invention 1. Definitions

[0030] In the following, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, publisher CRC Press, editor-in-chief DR Lide, 81st edition, 2000-2001). For example, group VIII according to the CAS classification corresponds to the metals of columns 8, 9 and 10 according to the new IUP AC classification.

[0031] In the present description, according to the IUP AC convention, micropores are pores with a diameter less than 2 nm, i.e. 0.002 pm, mesopores are pores with a diameter greater than or equal to 2 nm, i.e. 0.002 pm and less than 50 nm, i.e. 0.05 pm, and macropores are pores with a diameter greater than or equal to 50 nm, i.e. 0.05 pm.

[0032] Specific surface area means the specific surface area BET (SBet in m2 / g) determined by nitrogen adsorption in accordance with ASTM D 3663-78 established from the BRUNAUER-EMMETT-TELLER method described in the periodical "The Journal of American Society", 1938, 60, 309.

[0033] The total pore volume of the catalyst or support used for the preparation of the catalyst is understood to be the volume measured by intrusion with a mercury porosimeter according to ASTM D4284 at a maximum pressure of 4000 bars (400 MPa), using a surface tension of 484 dyne / cm and a contact angle of 140°, for example with an Autopore III model device from the brand Microméritics®.

[0034] The wetting angle was set at 140° following the recommendations of the book "Techniques de l'ingénieur, traité analyse et caractérisation", pages 1050-1055, written by Jean Charpin and Bernard Rasneur. In order to obtain better accuracy, the value of the total pore volume corresponds to the value of the total pore volume measured by intrusion with a mercury porosimeter measured on the sample at 4000 bars (400 MPa) minus the value of the total pore volume measured by intrusion with a mercury porosimeter measured on the same sample at a pressure corresponding to 2 bars (0.2 MPa).

[0035] The mean macropore diameter and mean macropore density within the substrate are determined from scanning electron microscopy (SEM) image processing, considering all pores with diameters between 0.05 µm and 30 µm. Scanning electron microscopy is used to quantify the number and mean diameter of macropores, for example, on a ZEISS Supra40® microscope. These samples are observed on polished sections using backscattered electrons (chemical contrast). The images were acquired using Multi SP software at magnifications of x30, x250, and x1000 to observe the substrate, for example, in the form of beads, in its entirety, and at x2500 for image analysis.Image analysis to determine the distribution of the average macropore diameter was performed using Plug im! software on 10 images taken at 2500x magnification of 5 different substrate samples, for example, 5 different beads, at a resolution of 2048 x 1536 pixels. The quantification method allows for the determination of the number and average diameter of macropores between 0.2 and 30 µm from images taken at 500x magnification. This macropore determination method is generally complemented or replaced by the so-called "small macropore quantification" method, which determines the number and average diameter of macropores between 0.05 and 0.5 µm from images taken at 2500x magnification. The total macropore area is scaled to the image area to obtain the macroporosity ratio. This apparent macroporosity rate on the image is considered identical to the volumetric macroporosity rate of the support.A skilled professional knows how to analyze enough images to obtain an average macropore density representative of the entire substrate.

[0036] The packed filling density (PHD) is measured as described in the book "Applied Heating" by G. Martino, J. Miquel, R. Montamal, A. Sugier, and H. Van Landeghem, Technip, Paris, 1987, chapter 6.2.4, pages 167-168. A graduated cylinder of acceptable dimensions is filled by successive additions, and between two successive additions, the catalyst is packed by shaking the cylinder until a constant volume is reached. This measurement is generally carried out on 1000 cm³ of catalyst or support packed into a cylinder with a height-to-diameter ratio close to 5:1. The apparent density of the packed product is calculated by dividing the introduced mass by the volume occupied after packing. The uncertainty in the measurement is generally on the order of ± 0.01 g / mL. This measurement can preferably be carried out on automated devices such as Autotap® is marketed by Quantachrome®.

[0037] The contents of metals, halogens and alkali or alkaline earth elements are measured by X-ray fluorescence.

[0038] By paraffinic compound (also called interchangeably paraffinic hydrocarbon or more simply paraffin), we mean hydrocarbon compounds of general empirical formula CnH2n+2.

[0039] By naphthenic compound (also called interchangeably naphthenic hydrocarbon or more simply naphthene), we mean hydrocarbon compounds comprising at least one saturated non-aromatic ring.

[0040] By activity, we mean the mass of paraffin converted expressed in grams of paraffin converted per gram of active metal per hour.

[0041] By selectivity, we mean the mass of olefins formed relative to the mass of all the products formed by conversion of paraffin.

[0042] By stability, we mean the stability of the activity which is generally measured by a percentage decrease in activity compared to an activity between 1 hour and at least 9 hours of testing.

[0043] Surface density refers to the quantity of atoms of the element considered per unit area, expressed in square nanometers, calculated from the mass content given by X-ray fluorescence analysis and the BET specific surface area of ​​the catalyst. It is expressed in atoms / nm² (or at / nm²). 2. Catalyst

[0044] The catalyst used in the process according to the invention comprises, preferably, an active phase based on at least one metal from Group VIII, at least one element M1 selected from tin, germanium, lead, gallium, indium, and thallium, and at least one element M2 selected from the alkali or alkaline earth elements, and a support comprising at least one refractory oxide, characterized in that the average macropore density of said support is greater than or equal to 2000 kpores / mm2 and less than 5000 kpores / mm2 and in that the packed filling density value of said support is between 0.50 g / mL and 0.68 g / ml.

[0045] Thanks to the combination of these very specific characteristics, namely an average macropore density associated with a packed filling density (PHD) value specific to the support, the catalyst exhibits improved performance in terms of activity, selectivity and stability for the dehydrogenation of paraffins and / or naphthenes and more particularly for the dehydrogenation of propane.

[0046] Advantageously, the content of group VIII metal, expressed as an element, is between 0.02% and 2% by weight relative to the total weight of the catalyst, preferably between 0.05% and 1.5% by weight, even more preferably between 0.1% and 0.8% by weight.

[0047] Advantageously, the metal from group VIII is chosen from platinum (Pt) or palladium (Pd), preferably platinum.

[0048] The group VIII metal can be present in the final catalyst in the form of oxide, sulfide, halide, oxyhalide, in chemical combination with one or more of the other components of the catalyst or in the form of elemental metal.

[0049] Advantageously, the content of element Ml, selected from tin, germanium, lead, gallium, indium and thallium, expressed as an element, in the catalyst according to the invention is between 0.01% and 10% by weight relative to the total weight of the catalyst, more preferably between 0.05% and 5% by weight and most preferably between 0.1% and 1% by weight.

[0050] Preferably, the element Ml is tin (Sn).

[0051] The element Ml can exist in the catalyst in the form of oxide, sulfide, halide, oxyhalide, in chemical combination with one or more of the other components of the catalyst or in the form of elemental metal.

[0052] Advantageously, the content of element M2, chosen from the alkali or alkaline-earth elements, expressed as an element, in the catalyst according to the invention is between 0.4% and 8% weight relative to the total weight of the catalyst, more preferably between 0.45% and 6.0% weight, and very preferably between 0.5% and 3% weight.

[0053] Preferably, the element M2 is potassium (K) or cesium (Cs), and more preferably potassium.

[0054] When the element M2 is potassium, the potassium content, expressed as an element, in the catalyst according to the invention is advantageously between 0.5% and 3% by weight relative to the total weight of the catalyst, more preferably between 0.5% and 2.5% by weight, and very preferably between 0.5% and 2.25% by weight, and even more preferably between 0.65% and 0.95% by weight.

[0055] Advantageously, the surface density of element M2 in the catalyst according to the invention is between 0.5 atoms and 2 atoms of element M2 / nm2, more preferably between 0.55 atoms and 1.2 atoms of element M2 / nm2 and most preferably between 0.65 atoms and 1 atom of element M2 / nm2.

[0056] In an embodiment according to the invention, the catalyst comprises a halogen element (hereinafter referred to as X). The halogen content is advantageously between 0.75% and 5.5% by weight of halogen element relative to the total weight of the catalyst, more preferably between 0.85% and 4% by weight, and most preferably between 1% and 3.5% by weight.

[0057] Preferably, the halogen element is selected from the group consisting of fluorine, chlorine, bromine and iodine. Preferably, the halogen element is chlorine (Cl).

[0058] Advantageously, the surface density of halogen element in the catalyst is between 0.75 atoms and 5.5 atoms of element X / nm2, preferably between 0.85 atoms and 4 atoms of element X / nm2, more preferably between 1 atom and 3.5 atoms of element X / nm2 and most preferably between 1 atom and 2.45 atoms of element X / nm2.

[0059] Advantageously, the atomic ratio between the halogen element and the M2 element chosen from the alkali or alkaline earth compounds is between 1.5 and 3, and preferably between 1.5 and 2.5. Preferably, the halogen is chlorine and the alkali or alkaline earth is potassium.

[0060] In an embodiment according to the invention, the catalyst may further comprise phosphorus. The phosphorus may be present in the final catalyst as an oxide or mixed oxide compound, phosphate, polyphosphate, sulfide, halide, oxyhalide, hydride, in chemical combination with one or more of the other components of the catalyst.

[0061] In this embodiment, the phosphorus content, expressed as an element, in the catalyst is between 0.4% and 1% by weight relative to the total weight of the catalyst, preferably between 0.4% and 0.8% by weight.

[0062] All the elements (the group VIII metal, element M1, element M2, element X, optionally phosphorus) are preferably uniformly distributed in the support. This distribution is characterized by a Castaing microprobe analysis by determining a distribution coefficient between 0.8 and 1.1 for all the elements and preferably between 0.9 and 1.0 for all the elements.

[0063] The specific surface area of ​​the catalyst according to the invention is between 170 m2 / g and 250 m2 / g, preferably between 180 m2 / g and 220 m2 / g, preferably between 185 m2 / g and 220 m2 / g, more preferably between 185 m2 / g and 210 m2 / g, and even more preferably between 185 m2 / g and 195 m2 / g.

[0064] The catalyst advantageously has a total porous volume measured by mercury porosimetry of between 0.1 cm3 / g and 1.5 cm3 / g, preferably between 0.4 cm3 / g and 0.8 cm3 / g, and most preferably between 0.4 cm3 / g and 0.7 cm3 / g.

[0065] Advantageously, the catalyst has a packed filling density (DRT) value between 0.50 g / mL and 0.68 g / mL, preferably between 0.55 g / mL and 0.65 g / mL. 3. Support

[0066] The catalyst support comprises at least one refractory oxide. Preferably, said porous support is based on alumina, silica, or silica-alumina, more preferably based on alumina.

[0067] When the support is alumina-based, it is understood that it comprises at least 95% by weight, preferably at least 98% by weight, and particularly preferably at least 99% by weight of alumina relative to the weight of the support. The alumina generally has a crystallographic structure of the delta, gamma, or theta type, alone or in mixtures, more preferably of the gamma type.

[0068] Even more preferably, the support is made of alumina.

[0069] The specific surface area of ​​the support is between 170 m² / g and 250 m² / g, of preference between 180 m2 / g and 240 m2 / g, preferentially between 185 m2 / g and 230 m2 / g, more preferentially between 185 m2 / g and 220 m2 / g, and even more preferentially between 190 m2 / g and 220 m2 / g.

[0070] The support advantageously has a total porous volume measured by mercury porosimetry of between 0.1 cm3 / g and 1.5 cm3 / g, preferably between 0.4 cm3 / g and 0.8 cm3 / g, and most preferably between 0.4 cm3 / g and 0.7 cm3 / g.

[0071] Advantageously, the support has a packed filling density (DRT) value between 0.50 g / mL and 0.65 g / mL, preferably between 0.55 g / mL and 0.65 g / mL.

[0072] Advantageously, the catalyst support according to the invention comprises an average macropore density greater than or equal to 2000 kpores / mm2 and less than 5000 kpores / mm2, preferably between 2000 and 4500 kpores / mm2, and even more preferably between 2200 and 3500 kpores / mm2.

[0073] Advantageously, the catalyst support comprises macropores with an average diameter between 0.10 pm and 0.80 pm, preferably between 0.15 pm and 0.60 pm, and more preferably between 0.20 pm and 0.35 pm.

[0074] The support is advantageously in the form of beads, extrudates, pellets, or powder. Preferably, the support is in the form of beads. When the support is in the form of beads, its diameter is generally between 0.5 mm and 5 mm, preferably between 1 mm and 2 mm. When the support is present in the form of extradites, the diameter of the extradites is between 0.5 mm and 5 mm, preferably with a length-to-diameter ratio of 1:1 to 5:1.

[0075] The support can be obtained by any technique known to those skilled in the art. Shaping can be carried out, for example, by extrusion, pelletizing, the oil-drop method, rotary plate granulation, or any other method well known to those skilled in the art. Preferably, the support is obtained by the oil-drop method, as described in document FR3035798 AL 4. Process for preparing the catalyst

[0076] The catalyst according to the invention can be prepared using any technique known to those skilled in the art. When the catalyst support is alumina, the catalyst can be prepared by depositing its various components onto said alumina support. The deposition of each component can be carried out on the alumina support before or after shaping it. The components can be introduced successively in any order, from a single solution or from separate solutions. In the latter case, intermediate drying and / or calcination can be performed.

[0077] In a particular embodiment, the catalyst is prepared according to a preparation process comprising the following successive steps:

[0078] a) a support is prepared comprising the element Ml chosen from tin, germanium, lead, gallium, indium and thallium to obtain a first catalyst precursor;

[0079] b) the first catalyst precursor obtained in step a) is dried under a flow of a neutral gas or under a flow of a gas containing oxygen at a temperature less than or equal to 250°C, then calcined at a temperature between 350°C and 750°C to obtain a first dried and calcined catalyst precursor;

[0080] c) the first dried and calcined catalyst precursor obtained in step b) is impregnated with an impregnation solution comprising at least one precursor of at least one metal from group VIII, and optionally at least one precursor of an element X, and optionally phosphorus to obtain a second catalyst precursor;

[0081] d) the second catalyst precursor obtained in step c) is dried under a flow of a neutral gas or under a flow of a gas containing oxygen at a temperature less than or equal to 250°C, then calcined at a temperature between 350°C and 750°C to obtain a second dried and calcined catalyst precursor;

[0082] e) the second dried and calcined catalyst precursor obtained in step d) is impregnated with an impregnation solution comprising a precursor of at least one element M2, and optionally at least one precursor of an element X, to obtain a third catalyst precursor;

[0083] f) the third catalyst precursor obtained in step e) is dried under a flow of neutral gas or under a flow of oxygen-containing gas at a temperature less than or equal to 250°C, then calcined at a temperature between 350°C and 750°C;

[0084] g) Optionally, an oxychlorination step is carried out at a temperature between 350°C and 550°C and under a pressure between 0.1 MPa and 1.5 MPa, then calcined at a temperature between 350°C and 750°C. Group VIII Metal

[0085] Advantageously, the Group VIII metal is supplied to the support in any suitable manner, such as co-precipitation, ion exchange, or impregnation. Preferably, it is introduced by impregnation of the support, for example, by excess or dry impregnation (the volume of solution containing the element to be introduced corresponding to the porous volume of the support), and preferably by excess impregnation. For this purpose, the support is impregnated with an impregnation solution, aqueous or organic, or consisting of a mixture of water and at least one organic solvent, comprising at least one precursor of the Group VIII metal.

[0086] In general, hydrogen chloride or another similar acid may also be added to the impregnation solution to further facilitate the incorporation or fixation to the surface of the support of the group VIII metal and to promote a uniform distribution of the group VIII metal in the support.

[0087] When the Group VIII metal is platinum, the platinum precursors belong to the following group, without this list being exhaustive: hexachloroplatinic acid, bromoplatinic acid, ammonium chloroplatinate, platinum chlorides, such as PtCl2 or PtCl4, platinum dichlorocarbonyl dichloride, platinum tetraamine chloride, or dihydroxyplatinemia. Organic platinum complexes, such as platinum(II) diacetylacetonate, may also be used. These precursors may be used alone or in mixtures. Preferably, the precursor used is hexachloroplatinic acid. Element Ml

[0088] The element Ml chosen from tin, germanium, lead, gallium, indium and thallium can be supplied in any suitable way, such as co-precipitation, ion exchange or impregnation, and this at any stage of the catalyst preparation process.

[0089] According to a first embodiment, the element Ml can be introduced into the support, for example during the synthesis of the support or during the shaping of the support. Without being exhaustive, the techniques of addition before or during the dissolution of the oxide precursors of the support during the synthesis of the support, with or without During maturation, these methods may be suitable. The introduction can therefore be simultaneous or subsequent to the mixing of the support precursors. The Ml element can be introduced during support synthesis using a sol-gel technique or added to an alumina sol. The Ml element can also be introduced during support processing using prior art techniques such as extrusion or oil-drop forming.

[0090] According to a second embodiment, the element Ml can be introduced onto the substrate, for example by impregnating the substrate after it has been prepared. Impregnation of the substrate with a solution, aqueous or organic, or consisting of a mixture of water and at least one organic solvent, comprising one or more precursors of elements Ml, can be carried out by excess solution or by dry impregnation. Impregnation of the substrate with a solution containing one or more precursors of element Ml can be carried out before, after, or simultaneously with the impregnation of the Group VIII metal. Impregnation can be carried out in the presence of species that influence the interaction between the precursor of element Ml and the substrate.These species may be, for example, but not limited to, mineral acids (HCl, HNO3) or organic acids (carboxylic or polycarboxylic acid types), and organic compounds of the complexing type, as described for example in US patents 6,872,300 and 6,291,394. Preferably, the impregnation is carried out using any technique known to those skilled in the art that allows for a homogeneous distribution of the element Ml within the support.

[0091] According to a third variant, the element Ml can also be introduced partly during the synthesis or shaping of the support and partly by deposition on the shaped support.

[0092] Preferably, the element Ml is introduced into the support, i.e., during the synthesis of the support or during the shaping of the support. In the case of an alumina-based support in the form of beads prepared by the draining technique, the precursor of the element Ml is introduced into the suspension to be drained.

[0093] The precursors of element Ml can be mineral or organometallic, possibly water-soluble organometallic. The precursor of element Ml can be selected from the group consisting of halogenated compounds, hydroxides, carbonates, carboxylates, sulfates, tartrates, and nitrates. These forms of element Ml can be introduced into the catalyst preparation medium as is or generated in situ (for example, by the introduction of tin and a carboxylic acid). When element Ml is tin, tin-based organometallic precursors can be selected, for example, from the following list: SnlU, where R represents an alkyl group, for example, the butyl group, Me3SnCl, Me2SnCl2, Et3SnCl, Et2SnCl2, EtSnCl3, iPrSnCl2 and the hydroxides Me3SnOH, Me2Sn(OH)2, Et3SnOH, Et2Sn(OH)2, the oxides (Bu3Sn)2O, and the acetate Bu3SnOC(O)Me. Preferably, tin halogenated species, particularly chlorinated ones, are used. Even more preferably, the precursor of element M1 is SnCl2 or SnCl4. Element M2

[0094] The element M2, selected from among the alkali or alkaline earth elements, can be supplied in any suitable manner, such as coprecipitation, ion exchange, or impregnation, at any stage of the catalyst preparation process. In particular, it can be introduced according to the three variants described for element M1. Preferably, it is introduced by impregnation, either dry or in excess, preferably in excess, and particularly preferably, it is introduced after the introduction of the Group VIII metal as described above.

[0095] The precursor(s) of element M2, chosen from among the alkali or alkaline earth elements, may be selected from hydroxides, halides, nitrates, and carbonates. When element M2 is potassium, the precursor(s) may be selected from KOH, KCl, KN03, K2CO3, or K2PtCl6. Element X (optional)

[0096] The element X chosen from among the halogens can be supplied in any suitable manner, such as coprecipitation, ion exchange, or impregnation, at any stage of the catalyst preparation process. In particular, it can be introduced according to the three variants described in the case of element ML

[0097] In a preferred embodiment, element X is chlorine. Chlorine is introduced by impregnation, and particularly preferably, it is introduced by impregnation simultaneously with the Group VIII metal or prior to the impregnation of the Group VIII metal. As a possible counter-anion of compounds comprising element M1, the Group VIII metal, and element M2, chlorine can also be introduced simultaneously with these elements, for example, by using precursors of the type H2PtCl6, SnCl2, or KCl1, or by treating the support in one of the preparation steps with hydrochloric acid. Chlorine can also be supplied in the preparation process by an additional oxychlorination step. Phosphorus (optional)

[0098] Phosphorus can be supplied in any suitable manner, such as coprecipitation, ion exchange, or impregnation, at any stage of the catalyst preparation process. In particular, it can be introduced according to the three variants described in the case of element ML

[0099] According to one embodiment, the phosphorus is introduced into the support, i.e. during its shaping, for example simultaneously with the ML element

[0100] According to another embodiment, the phosphorus is introduced by impregnation, and particularly preferably it is introduced by impregnation at the same time as the group VIII metal. In this case, the impregnation solution contains the precursor of the group VIII metal and the precursor of the phosphorus.

[0101] The precursors of phosphorus can be acids or salts, and can be chosen from the following compounds: H3PO4, H3PO3, H3PO2, NH4H2PO4, or (NH4)2 HPO4. Order of introduction of precursors

[0102] As described above, the catalyst preparation process according to the invention comprises several embodiments, distinguished in particular by the order of introduction of the Group VIII metal, element M1, element M2, element X, and optionally phosphorus onto and / or into the support, i.e., during the synthesis of the support or during the shaping of the support. The catalyst preparation process includes the simultaneous or successive introduction, in any order, of the Group VIII metal, element M1, element M2, and optionally phosphorus and / or element X onto and / or into the support.

[0103] When element M1 and / or element M2 and / or optionally phosphorus and / or element X are introduced into the support, i.e., during support synthesis or support shaping, the preparation process generally includes a drying step and a calcination step before the deposition of the Group VIII metal. Drying is generally carried out at a temperature of 250°C or lower, preferably between 50°C and 250°C, more preferably between 70°C and 200°C, under air or an inert atmosphere. Calcination is preferably carried out at a temperature between 350°C and 750°C, preferably between 400°C and 650°C, and even more preferably between 500°C and 600°C. The temperature rise can be regular or include intermediate temperature plateaus, these plateaus being reached with fixed or variable temperature rise rates.These temperature increases can therefore be identical or differ in their rate (in degrees per minute or per hour). The gas atmosphere used during calcination contains oxygen. Air can therefore also be used during this calcination stage. The calcination gas may also contain water.

[0104] When one or more elements from among the group VIII metal, element M1, element M2, element X and / or optionally phosphorus, are introduced onto the shaped support, preferably by dry or excess impregnation, the introduction of said elements may be simultaneous by a single impregnation solution or have place separately by several impregnation solutions containing one or more of the components and this in any order.

[0105] Any impregnation solution described in the present invention may comprise any polar solvent known to those skilled in the art. The polar solvent used is advantageously chosen from the group consisting of methanol, ethanol, water, phenol, and cyclohexanol, alone or in mixtures. The polar solvent may also advantageously be chosen from the group consisting of propylene carbonate, DMSO (dimethyl sulfoxide), N-methylpyrrolidone (NMP), or sulfolane, alone or in mixtures. Preferably, a polar protic solvent is used. A list of common polar solvents and their dielectric constants can be found in the book "Solvents and Solvent Effects in Organic Chemistry," C. Reichardt, Wiley-VCH, 3rd edition, 2003, pages 472-474. Most preferably, the solvent used is water or ethanol, and particularly preferably, the solvent is water.

[0106] After each impregnation step, the resulting catalyst precursor is preferably dried to remove all or part of the solvent introduced during impregnation, preferably at a temperature below 250°C, more preferably between 50°C and 250°C, and even more preferably between 70°C and 200°C. Drying is advantageously carried out for a period of between 1 and 24 hours, preferably between 1 and 20 hours. Drying is performed under air or under an inert atmosphere (nitrogen, for example). After the drying step, the catalyst is preferably calcined, generally under air. Calcination is preferably carried out at a temperature between 350°C and 750°C, and more preferably between 400°C and 650°C, and even more preferably between 500°C and 600°C. The temperature ramp may optionally include temperature plateaus.The calcination time is generally between 0.5 and 16 hours, preferably between 1 and 5 hours. The gas atmosphere used during calcination contains oxygen. Air can therefore also be used during this calcination stage. The calcination gas may optionally contain water.

[0107] In a particular embodiment, the catalyst is prepared according to a preparation process comprising the following successive steps:

[0108] a) a support is prepared comprising the element Ml chosen from tin, germanium, lead, gallium, indium and thallium to obtain a first catalyst precursor;

[0109] b) the first catalyst precursor obtained in step a) is dried under a flow of a neutral gas or under a flow of a gas containing oxygen at a temperature less than or equal to 250°C, then calcined at a temperature between 350°C and 750°C to obtain a first dried and calcined catalyst precursor;

[0110] c) the first dried and calcined catalyst precursor obtained in step b) is impregnated with an impregnation solution comprising at least one precursor of at least one metal from group VIII, and optionally at least one precursor of an element X, and optionally phosphorus to obtain a second catalyst precursor;

[0111] d) the second catalyst precursor obtained in step c) is dried under a flow of a neutral gas or under a flow of a gas containing oxygen at a temperature less than or equal to 250°C, then calcined at a temperature between 350°C and 750°C to obtain a second dried and calcined catalyst precursor;

[0112] e) the second dried and calcined catalyst precursor obtained in step d) is impregnated with an impregnation solution comprising a precursor of at least one element M2, and optionally at least one precursor of an element X, to obtain a third catalyst precursor;

[0113] f) the third catalyst precursor obtained in step e) is dried under a flow of neutral gas or under a flow of oxygen-containing gas at a temperature less than or equal to 250°C, then calcined at a temperature between 350°C and 750°C;

[0114] g) Optionally, an oxychlorination step is carried out at a temperature between 350°C and 550°C and under a pressure between 0.1 MPa and 1.5 MPa, then calcined at a temperature between 350°C and 750°C.

[0115] In an embodiment according to the invention, when element X is chlorine, said chlorine element is supplied at least once either at step c) and / or at step e), and / or at step g).

[0116] Preferably, the introduction of the element M2, chosen from among the alkali or alkaline earth elements, and more particularly potassium, is carried out on a catalyst precursor comprising the group VIII metal, more particularly platinum, which has been previously dried and calcined. In fact, introducing potassium after platinum prevents the platinum from being leached out during the impregnation of the group VIII metal.

[0117] In step a), a support comprising element Ml, preferably tin, is prepared. Element Ml, preferably tin, can be introduced at any time during the preparation of the support, and preferably during shaping, or by impregnation onto an already formed support. Preferably, element Ml is introduced during the shaping of the support.

[0118] Similarly, phosphorus can be introduced at any time during the preparation of the substrate, and preferably during shaping, or by impregnation onto an already formed substrate. According to one embodiment, phosphorus is introduced into the substrate, i.e., during the shaping of the substrate, preferably with the element Ml, preferably tin. According to another embodiment, phosphorus is introduced by impregnation, and in a particularly preferred manner it is introduced by impregnation at the same time as the metal of group VIII.

[0119] The introduction of the group VIII metal can advantageously be carried out by one or more excess impregnations of solution on the support, or by one or more dry impregnations, and, preferably, by a single excess impregnation of said support (preferably containing the element Ml, preferably tin, and possibly phosphorus), using solution(s), preferably aqueous, containing the precursor of the group VIII metal and possibly the precursor of phosphorus (when the support does not contain or only partially contains phosphorus).

[0120] In step e), the second dried and calcined catalyst precursor obtained in step d) is impregnated with an impregnation solution comprising at least one precursor of an element M2 selected from the alkali or alkaline earth elements. The introduction of the alkali or alkaline earth element(s) can advantageously be carried out by one or more excess impregnations of the solution onto the support, or by one or more dry impregnations, and preferably by a single dry or excess impregnation of said precursor, using solution(s), preferably aqueous, containing at least one precursor of the alkali or alkaline earth element, and preferably at least one potassium precursor.

[0121] In the optional step g), chlorine is supplied by means of an oxychlorination treatment. Such a treatment can, for example, be carried out at a temperature between 350°C and 550°C and under a pressure between 0.1 MPa and 1.5 MPa, for a duration preferably between 30 minutes and 10 hours, and under an air flow containing the desired quantity of chlorine and possibly containing water.

[0122] According to another embodiment, the catalyst according to the invention can be prepared by preparing a support comprising tin by introducing the tin precursor during the shaping of the support, followed by one or more excess impregnations of solution on the support, or by one or more dry impregnations, using solution(s), preferably aqueous, containing a precursor of a group VIII metal, a phosphorus precursor and a precursor of an alkali or alkaline earth element and preferably a potassium precursor, alone or in mixture, then drying and calcining under the conditions described above.

[0123] When the various precursors used in the preparation of the catalyst according to the invention do not contain halogens or contain halogens in insufficient quantities, it may be necessary to add a halogenated compound during preparation. Any compound known to those skilled in the art can be used and incorporated into any of the steps in the preparation of the catalyst according to the invention. In particular, it is possible to use organic compounds such as halides. of methyl or ethyl, for example dichloromethane, dichloroethane, dichloropropane, chloroform, methyl chloroform or carbon tetrachloride.

[0124] The halogen can also be added by means of impregnation with an aqueous solution of the corresponding acid, for example hydrochloric acid, at any time during the preparation. A typical procedure involves impregnating the solid to introduce the desired amount of halogen. The catalyst is kept in contact with the aqueous solution for a sufficiently long time to deposit this amount of halogen. Additional reduction step (optional)

[0125] In an embodiment according to the invention, prior to using the catalyst in the catalytic reactor and implementing a dehydrogenation process, a reduction treatment step is carried out in the presence of a reducing gas so as to obtain a catalyst comprising said Group VIII metal and said element Ml at least partially in metallic form. This step is advantageously carried out in-situ, that is, after loading the catalyst into a dehydrogenation reactor. Carrying out the reduction treatment of the catalyst in-situ eliminates the need for an additional step of passivating the catalyst with an oxygenated compound or with CO2, which is necessarily the case when the catalyst is prepared by carrying out an ex-situ reduction treatment, that is, outside the reactor used for dehydrogenation.Indeed, when the reduction treatment is carried out ex-situ, it is necessary to carry out a passivation step in order to preserve the metallic phase of the catalyst in the presence of air (during the transport and loading operations of the catalyst into the hydrogenation reactor), and then to carry out a new reduction step of the catalyst in-situ.

[0126] The reducing gas is preferably hydrogen. Hydrogen can be used pure or in a mixture (for example, a hydrogen / nitrogen, hydrogen / argon, or hydrogen / methane mixture). When hydrogen is used in a mixture, any proportion is possible.

[0127] Preferably, said reduction treatment is carried out at a temperature between 100°C and 600°C, and preferably between 200°C and 580°C, under a stream of pure or diluted hydrogen, up to the maximum reduction temperature, followed by holding, for example, for 30 minutes to 6 hours at that temperature. The temperature rise to the desired reduction temperature is generally slow, for example, set between 0.1 and 10°C / min, preferably between 0.3 and 7°C / min.

[0128] The hydrogen flow rate, expressed in L / hour / gram of catalyst precursor, is between 0.01 and 100 L / hour / gram of catalyst, preferably between 0.05 and 10 L / hour / gram of catalyst precursor, even more preferably between 0.1 and 5 L / hour / gram of catalyst precursor. Passivation step (optional)

[0129] The process according to the invention may advantageously include a passivation step using a sulfur compound, which improves the selectivity of the catalysts and prevents thermal runaway during the start-up of new catalysts (known as "run-away" in English terminology). The passivation step is carried out using methods known to those skilled in the art.

[0130] The passivation step with a sulfur compound is generally carried out at a temperature between 20 and 350°C, preferably between 40 and 200°C, for 10 to 240 minutes. The sulfur compound is, for example, chosen from the following: thiophene, thiophane, alkyl monosulfides such as dimethyl sulfide, diethyl sulfide, dipropyl sulfide, and propylmethyl sulfide, or an organic disulfide of the formula HO-Ri-SS-R2-OH such as di-thio-diethanol of the formula HO-C2H4-SS-C2H4-OH (often called DEODS). The sulfur content is generally between 0.1 and 2% by weight of said element relative to the total weight of the catalyst.

[0131] 5. Process for dehydrogenating paraffins and / or naphthenes

[0132] The invention also relates to a process for dehydrogenating a hydrocarbon feed comprising paraffinic and / or naphthenic compounds in the presence of the catalyst according to the invention.

[0133] The processes for dehydrogenating paraffins and / or naphthenes make it possible to selectively produce olefins and contribute to the production of significant quantities of hydrogen essential for the hydrogenation and hydrotreating processes of a petrochemical complex or refinery.

[0134] The hydrocarbon filler generally comprises paraffinic and / or naphthenic compounds containing from 2 to 30 carbon atoms per molecule, alone or in mixtures. More particularly, the hydrocarbon filler comprises paraffinic and / or naphthenic compounds having from 2 to 15 carbon atoms per molecule, preferably paraffinic compounds having from 2 to 5 carbon atoms per molecule, such as propane, n-butane, n-pentane, isomers of butane and pentane or mixtures thereof, and / or preferably naphthenic compounds having from 5 to 12 carbon atoms such as cyclohexane, methylcyclohexane, decalin or mixtures thereof. The filler may also comprise unsaturated hydrocarbons having from 2 to 15 carbon atoms per molecule.

[0135] Typically, the dehydrogenation catalyst is loaded into a unit and previously subjected to a reduction treatment as described above. It can be implemented in any manner known to those skilled in the art. For example, it can be implemented in a fixed bed or a moving bed, preferably a moving bed. According to one embodiment of the invention, the dehydrogenation catalyst is implemented in several reactors installed in series.

[0136] The various processes for dehydrogenating paraffins and naphthenes differ in the choice of operating conditions and the composition of the feedstock. The adjustment of the operating conditions, depending on the nature of the feedstock to be treated, is carried out in such a way as to obtain the best pressure-temperature-yield and activity ratio in a manner known to those skilled in the art.

[0137] Generally, the process of dehydrogenating a hydrocarbon feed comprising paraffins and / or naphthenes is carried out at a pressure between 0.1 MPa and 4 MPa, at a temperature between 200°C and 800°C and with a liquid hourly space velocity (LHSV) between 0.5 h1 and 50 h1.

[0138] More specifically, the dehydrogenation reaction of paraffins is carried out at a pressure between 0.1 MPa and 4 MPa, and more preferably between 0.25 MPa and 3.0 MPa, and at a temperature between 400°C and 800°C, depending on the nature of the feedstock. The temperature is advantageously between 560°C and 700°C for a feedstock consisting mainly of propane, between 450°C and 600°C for a feedstock consisting mainly of isobutane, and between 400°C and 550°C for a feedstock consisting mainly of isopentane. It may be advantageous to use hydrogen as a diluent. The hydrogen / hydrocarbon molar ratio of the feedstock is generally between 0.1 and 10, preferably between 0.5 and 8.The liquid volumetric space velocity of hydrocarbon feed (LHSV or Liquid Hourly Space Velocity according to Anglo-Saxon terminology), the unit of which is in liters of hydrocarbon feed per liter of catalyst per hour, is preferably between 0.5 h1 to 50 h1, more preferably between 1.5 h1 to 15 h1. .

[0139] More specifically, the dehydrogenation reaction of naphthenes takes place at a pressure between 0.1 MPa and 2 MPa, preferably between 0.1 MPa and 1 MPa, and at a temperature between 200°C and 400°C. The liquid hourly space velocity (LHSV) of the hydrocarbon feed, the unit of which is liters of hydrocarbon feed per liter of catalyst per hour, is generally between 0.5 h⁻¹ and 50 h⁻¹.

[0140] The catalyst according to the invention is regenerable by at least one combustion step under an oxidizing medium.

[0141] The catalyst regeneration is carried out in a cyclic or continuous system. It may consist of a simple combustion of the coke deposits. This combustion operation is usually performed by injecting air into an inert mixture. The oxygen content in the gas at the regeneration inlet is preferably between 0.1% and 2% by volume. Combustion is usually carried out at a temperature between 350°C and 550°C and under a pressure between 0.1 MPa and 1.5 MPa.

[0142] Combustion may optionally be preceded by an operation of stripping the sulfur contained in the catalyst in the case where the catalyst includes sulfur introduced by injection of DMDS for example.

[0143] The regeneration process may also include, following the coke combustion step, an oxyhalogenation step of the catalyst, preferably oxychlorination. For this purpose, the oxygen content in the gas at the regeneration inlet is increased by at least 10% compared to the value in the preceding combustion step. At least one halogenated derivative, i.e., at least one halogen and / or a halogenated compound, is introduced simultaneously. Chlorine and / or a chlorinated compound are preferably used. The proportion of halogen and / or halogenated compound(s) used is such that 0.2% to 3.5% by weight of a halogenated alumina derivative can be formed relative to the catalyst undergoing regeneration. The oxyhalogenation is carried out at a temperature between 350°C and 550°C and under a pressure between 0.1 MPa and 1.5 MPa.A catalyst calcination step is generally carried out after oxyhalogenation, during which the oxygen content in the gas at the regeneration inlet is between 3% and 20% by volume, the average temperature is between 350°C and 550°C and the pressure is between 0.1 MPa and 1.5 MPa.

[0144] Before subjecting the regenerated catalyst to the reaction conditions, it undergoes a preliminary reduction under a hydrogen-containing gas, preferably pure hydrogen. This reduction can be carried out in the regeneration chamber if it is separate from the reaction chamber, in the reaction chamber itself, or in an intermediate zone separate from the regeneration and reaction zones. If this reduction has not been carried out prior to the reaction, it can also occur in the reaction chamber after the reaction has started: the initial stages of the reaction then serve to transform the catalyst into a catalytically active form for dehydrogenation. The reduction is carried out under a stream of hydrogen-containing gas, preferably pure hydrogen, at a temperature between 100°C and 600°C and at a pressure between 0.2 MPa and 2.5 MPa, preferably between 0.4 MPa and 1.5 MPa.

[0145] Possible sulfidation of the catalyst may follow this reduction step and therefore precede the dehydrogenation reaction itself.

[0146] All or part of the hydrogen produced can be recycled at the inlet of the dehydrogenation reactor. All or part of the unconverted propane can be recycled at the inlet of the dehydrogenation reactor. Examples

[0147] The following examples illustrate the invention without limiting its scope.

[0148] Example 1: Preparation of catalysts A, B, C and D with supports Al, Bl, Cl and DI

[0149] Catalysts A to D are all prepared using the same method from supports Al, B1, Cl and DI whose textural properties are described in Table 1 below.

[0150] [Tables 1] Support Sbet (m² / g) DRT (g / ml) Mean macropore diameter ux (pm) Macropore density (kpores / mm²) Al 191 0.69 0.37 460 Bl 200 0.70 0.22 437 Cl 218 0.58 0.27 2326 DI 190 0.60 0.22 3456

[0151] Scanning Electron Microscopy images of polished sections are shown below. They were taken at a magnification of x2500 and a resolution of 2048x1536 pixels.

[0152] To 100 grams of alumina support containing Al, Bl, Cl, and Di and containing tin, 400 cm³ of an aqueous solution of hexachloroplatinic acid and hydrochloric acid is added by excess impregnation. The support is left in contact for 4 hours and then drained. It is dried at 120°C for 15 hours and then calcined at 500°C under an air flow of 100 liters per hour for 3 hours, with a temperature rise rate of 7°C per minute.

[0153] To 100 grams of this calcined solid, 75 cm³ of a potassium carbonate solution of suitable concentration is added by dry impregnation. The mixture is allowed to mature, then dried at 120°C for 15 hours and calcined at 500°C under an air flow of 100 liters per hour for 3 hours, with a temperature rise rate of 7°C per minute.

[0154] The catalysts A, B, C and D obtained after calcination all contain 0.30 wt% platinum, 0.29 wt% tin relative to the total weight of the catalyst, 1.33 atCl / nm2 and 0.75 atK / nm2. Their characteristics are described in Table 2 below.

[0155] [Tables2] Catalyst Cl content (% by weight) K content (% by weight) A 1.50 0.93 B 1.57 0.97 C 1.71 1.06 D 1.50 0.93

[0156] Example 2: Process for dehydrogenating propane using catalysts A to D

[0157] 10 cm3 of catalyst are introduced into a reactor equipped with a shell electric heating. The gas flows are sent in downflow, that is to say from top to bottom relative to the catalytic bed.

[0158] The reduction step is carried out according to the following protocol: the catalyst is heated under an inert gas to 150°C with a ramp of 5°C / min and then maintained at 150°C for 1.5 hours. The inert gas is replaced by hydrogen and the temperature is raised to 635°C with a ramp of 5°C / min and then maintained at 635°C for 9.5 hours. The reduction step is then complete and the hydrogen flow rate is set at 28 L / h.

[0159] The propane flow rate is in turn set to 28 L / h, corresponding to a LHSV of 10.8 h⁻¹. This flow rate setting corresponds to the initial reaction time. The gaseous effluent is analyzed by gas chromatography, calculating the volume and mass proportions of each compound. The major products formed, which are used in the selectivity calculation, are methane, ethane, ethylene, propylene, and benzene.

[0160] The conversion is calculated by taking the ratio of the mass quantity of products formed analyzed in the effluent to the mass quantity of propane injected.

[0161] The activity is calculated by determining the mass quantity of propane converted per gram of platinum per hour.

[0162] The propylene selectivity is calculated by dividing the mass amount of propylene formed by the sum of the mass amounts of all the reaction products at a propane conversion level of 28 wt%.

[0163] Benzene selectivity is calculated by dividing the mass of benzene formed by the sum of the mass amounts of all the reaction products at a propane conversion level of 28 wt%. Benzene selectivity is particularly informative regarding the catalyst's propensity to produce coke and to deactivate: the higher the selectivity, the more readily the catalyst cokes.

[0164] Stability is determined by comparing the initial activity of the catalyst with the activity at 9 hours of TOS (Time on Stream): % loss of activity = ((activity at 1 hour of TOS) - (activity at 9 hours of TOS)) / (activity at 1 hour of TOS).

[0165] Table 3 below reports the activities after 1 and 9 hours of "Time On Stream", the percentage loss of activity between 1 hour and 9 hours of TOS and the maximum selectivities obtained in propylene and benzene.

[0166] [Tables3] Catalyst Activity at 1 hour of TOS gC3 / gPt / h Activity at 9 hours of TOS gC3 / gPt / h Loss of activity (%) Propylene selectivity (% wt) Benzene selectivity (% wt) A (non-compliant) 770 678 11.9 95.4 0.39 B (non-compliant) 685 540 21.2 95.2 0.58 C (compliant) 1040 930 10.5 96.1 0.14 D (compliant) 1094 997 8.9 96.4 0.12

[0167] The performance of the non-compliant catalysts A and B, which do not meet the macropore density and DRT requirements, clearly demonstrates a deficit in activity and propylene selectivity, and a high value of benzene selectivity, compared to the catalysts according to the invention. Furthermore, the deactivation of these catalysts is greater compared to the catalysts according to the invention.

[0168] The performance of catalysts C and D according to the invention, respecting the conditions of macropore density and DRT, is the best in terms of activity, propylene selectivity and stability with low benzene selectivity values ​​compared to non-conforming catalysts.

Claims

Demands

1. A process for dehydrogenating a hydrocarbon feed comprising paraffins and / or naphthenes, wherein said feed is contacted with a catalyst at a pressure between 0.1 MPa and 4 MPa, at a temperature between 200°C and 800°C, and with a liquid volumetric space velocity between 0.5 h₁ and 50 h₂, said catalyst comprising an active phase based on at least one Group VIII metal, at least one element M₁ selected from tin, germanium, lead, gallium, indium, and thallium, and at least one element M₂ selected from the alkali or alkaline earth elements, and an alumina support, characterized in that the average macropore density of said support is greater than or equal to 2000 kpores / mm² and less than 5000 kpores / mm², and in that the packed filling density value (DRT) of said support is between 0.50 g / mL and 0.68 g / mL,in that the specific surface area of ​​the support is between 190 m² / g and 220 m² / g, and in that the average macroporous diameter of said support is between 0.10 pm and 0.80 pm.

2. A method according to the preceding claim, characterized in that the packed filling density (DRT) value of said support is between 0.55 g / mL and 0.65 g / mL.

3. A process according to any one of the preceding claims, characterized in that the content of group VIII metal is between 0.02% and 2% by elemental weight of group VIII metal relative to the total weight of the catalyst.

4. A method according to any one of the preceding claims, characterized in that the group VIII metal is platinum.

5. A process according to any one of the preceding claims, characterized in that the content of element Ml is between 0.01% and 10% by elemental weight of element Ml relative to the total weight of the catalyst.

6. A method according to any one of the preceding claims, characterized in that the element Ml is tin.

7. A method according to any one of the preceding claims, characterized in that the surface density of element M2 is between 0.5 atoms and 2 atoms of element M2 / nm2.

8. A method according to any one of the preceding claims, characterized in that the element M2 selected from the alkali or alkaline-earth elements is potassium.

9. A process according to claim 8, characterized in that the potassium content, expressed as an element, is between 0.5% and 3% by weight relative to the total weight of the catalyst.

10. A process according to any one of the preceding claims, wherein the hydrocarbon filler comprises paraffinic and / or naphthenic compounds containing from 2 to 30 carbon atoms per molecule, taken alone or in mixture.

11. A process according to claim 10, wherein the hydrocarbon filler comprises paraffinic compounds having 2 to 5 carbon atoms per molecule and / or nathenic compounds having 5 to 12 carbon atoms.

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