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  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/08—Heat treatment
  • B01J37/10—Heat treatment in the presence of water, e.g. steam
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  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
  • B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
  • B01J29/74—Noble metals
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  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
  • B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
  • B01J29/7269—MTW-type, e.g. ZSM-12, NU-13, TPZ-12 or Theta-3
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  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
  • B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
  • B01J29/74—Noble metals
  • B01J29/7469—MTW-type, e.g. ZSM-12, NU-13, TPZ-12 or Theta-3
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  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
  • B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
  • B01J29/76—Iron group metals or copper
  • B01J29/7669—MTW-type, e.g. ZSM-12, NU-13, TPZ-12 or Theta-3
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  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/63—Pore volume
  • B01J35/635—0.5-1.0 ml/g
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/63—Pore volume
  • B01J35/638—Pore volume more than 1.0 ml/g
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/66—Pore distribution
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/0201—Impregnation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/08—Heat treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/16—Reducing
  • B01J37/18—Reducing with gases containing free hydrogen
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
  • C07C5/22—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by isomerisation
  • C07C5/27—Rearrangement of carbon atoms in the hydrocarbon skeleton
  • C07C5/2729—Changing the branching point of an open chain or the point of substitution on a ring
  • C07C5/2732—Catalytic processes
  • C07C5/2737—Catalytic processes with crystalline alumino-silicates, e.g. molecular sieves
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
  • C07C5/22—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by isomerisation
  • C07C5/27—Rearrangement of carbon atoms in the hydrocarbon skeleton
  • C07C5/2767—Changing the number of side-chains
  • C07C5/277—Catalytic processes
  • C07C5/2775—Catalytic processes with crystalline alumino-silicates, e.g. molecular sieves
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
  • B01J2229/10—After treatment, characterised by the effect to be obtained
  • B01J2229/14—After treatment, characterised by the effect to be obtained to alter the inside of the molecular sieve channels
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
  • B01J2229/10—After treatment, characterised by the effect to be obtained
  • B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
  • B01J2229/30—After treatment, characterised by the means used
  • B01J2229/36—Steaming
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
  • B01J2229/30—After treatment, characterised by the means used
  • B01J2229/42—Addition of matrix or binder particles
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2529/00—Catalysts comprising molecular sieves
  • C07C2529/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites, pillared clays
  • C07C2529/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • C07C2529/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups C07C2529/08 - C07C2529/65
  • C07C2529/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups C07C2529/08 - C07C2529/65 containing iron group metals, noble metals or copper
  • C07C2529/74—Noble metals
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals
  • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Definitions

• the present invention relates to a catalyst comprising a zeolite of structural type MTW, modified by a steam treatment.
• the invention also relates to the preparation of the catalyst according to the invention and the use of said catalyst in a process for the isomerization of aromatic compounds containing 8 carbon atoms per molecule.
• the isomerization process is particularly applicable to the isomerization of aromatic compounds containing 8 carbon atoms per molecule in paraxylene and more particularly to the isomerization of ethylbenzene to paraxylene.
• the isomerization of the aromatic C8 cut is the main route of formation of paraxylene, a product that is highly sought after in the petrochemical industry, used in particular for the manufacture of polyester fibers and films.
• the aromatic C8 cut resulting from catalytic reforming or steam-cracking comprises meta, para, ortho-xylene and ethylbenzene.
• the cost of the distillative separation of ethylbenzene being too high, only paraxylene and optionally ortho-xylene are separated by selective separation on zeolites according to different separation processes.
• the C8 residual cut comprising ethylbenzene is then converted into an isomerization unit, the objective being to maximize the paraxylene fraction and convert the ethylbenzene into xylenes or benzene.
• the isomerization of xylenes occurs by an acid monofunctional mechanism, the acid function being generally provided by a zeolite.
• the transformation of ethylbenzene requires a bifunctional catalyst having both an acid function and a hydrogenating function.
• Ethylbenzene is either isomerized to xylenes or is dealkylated to benzene. This is called either isomerizing isomerization or isomerization isomerization.
• the catalysts employed are generally bifunctional catalysts combining a zeolite phase, at least one metal and a binder (also called matrix).
• An improvement of the zeolite catalysts in isomerizing isomerization to xylenes would consist in increasing the conversion of ethylbenzene, the most difficult step of this transformation.
• secondary parasitic reactions such as disproportionation and dealkylation of ethylbenzene limit the recovery of this compound to xylenes.
• One way of improvement is to modify the catalyst by different treatments which can cause changes in the characteristics of the zeolite and / or the binder used.
• a particular treatment is the treatment with steam (or steaming according to the English terminology).
• No. 4,784,747 discloses steam-treated catalysts, which makes it possible to increase the catalytic activity, in particular by cracking and dewaxing. The best performances have been obtained for a steam treatment between 200 and 500 ° C.
• a zeolitic catalyst comprising at least one MTW zeolite having undergone a particular treatment in the presence of water vapor showed a strong improvement in conversion to ethylbenzene and the thermodynamic equilibrium approach of paraxylene when used in an isomerization isomerization process of an aromatic C8 cut comprising at least ethylbenzene.
• the present invention relates to a catalyst comprising at least one MTW structural type zeolite, a matrix, at least one Group VIII metal of the periodic table of elements (corresponding to groups 8 to 10 of the new periodic classification of the elements, CRC Handbook of Chemistry and Physics, 200-2001), said catalyst having a mesoporous volume increased by at least 10%, preferably at least 10.5% with respect to its initial mesoporous volume (included generally between 0.55 and 0.75 mL / g) after treatment with steam at a partial pressure of between 0.01 and 0.07 MPa and at a temperature between 300 and 400 ° C for at least 0.5 hours.
• the mesoporous volume of the catalyst is obtained by subtracting the microporous volume from the pore volume of the catalyst.
• microporous volume and the pore volume are determined from the nitrogen adsorption isotherm, respectively by the t method and by the adsorbed nitrogen volume (mL / g) at a relative pressure of 0.95, according to the book Adsorption by Powders, F.Rouquerol et al., Academy Press 1999.
• this increase in conversion may be related in part to the increase in the mesoporous volume of the catalyst resulting from the steam treatment as described above.
• the steam treatment is carried out with a partial pressure of steam of between 0.04 and 0.06 MPa, preferably diluted in air.
• the steam treatment is carried out at a temperature of between 300 and 380 ° C. for 0.5 hour and 24 hours, preferably between 1 hour and 12 hours.
• the MTW structural type zeolite used is preferably a zeolite selected from the group consisting of zeolites ZSM-12, CZH-5, NU-13, TPZ-12, Theta-3 and VS-12, preferably zeolite. is zeolite ZSM-12.
• Zeolite ZSM-12 is a well-known zeolite having an aluminosilicate-based structure and possibly including one or more other elements. Many methods for obtaining this zeolite are known and are available in the prior art. A definition of ZSM-12 is given in the "Database of zeolite structures" published in 2007/2008 by the "Structure Comission of the International Zeolite Association".
• the zeolite content is between 1 and 20% by weight relative to the weight of the support, the support corresponding to the mixture of the zeolite and the matrix.
• the catalyst according to the invention is preferably composed of:
• At least one zeolite of structural type MTW comprising silicon and at least one element T selected from the group formed by aluminum, iron, gallium and boron, with an Si / T atomic ratio of between 20 and 200 inclusive and preferably between 20 and 100 inclusive.
• said element T is chosen from the group consisting of aluminum and boron, more preferably element T is aluminum,
• the overall Si / Al atomic ratio determined by X-ray fluorescence or atomic absorption, takes into account both the aluminum atoms present in the zeolite framework and the aluminum atoms possibly present outside said zeolite framework, also called extra-lattice aluminum.
• the MTW structural type zeolite used has a Si / Al ratio of between 20 and 200 inclusive, preferably between 20 and 100 inclusive.
• the present invention also relates to a process for preparing the catalyst according to the invention.
• the catalyst according to the invention is prepared according to a process comprising the following steps:
• ii) preparing a support by shaping said zeolite with a matrix, iii) depositing at least one metal of group VIII of the periodic table of elements on said support or on said zeolite, the order of accomplishment of said steps ii ) and iii) being indifferent following said step i), iv) the catalyst resulting from stage ii) or stage iii) is brought into contact in the order of their production, with steam at a partial pressure of between 0.01 and 0.07 MPa, at a temperature between 300 and 400 ° C, for at least 0.5 hours, so that the mesoporous volume of the catalyst is increased by at least 10%, based on the initial mesoporous volume of the catalyst generally between 0.55 and 0.75 mL / g.
• the water vapor used is diluted in a neutral gas, dioxygen or in air.
• the MTW structural type zeolite used in step i) has a Si / Al ratio of between 20 and 200 inclusive, preferably between 20 and 100 inclusive.
• the zeolite of structural type MTW is shaped in step ii) with a matrix with a zeolite content between 1 and 20% by weight, preferably between 1 and 10% by weight relative to the mass of the support.
• the steam treatment of step iv) is carried out with a partial pressure of water vapor of between 0.04 and 0.06 MPa, preferably diluted in air.
• the steam treatment of step iv) is carried out at a temperature of between 300 and 380 ° C. for 0.5 hour to 24 hours, preferably between 1 hour and 12 hours.
• the flow rate of gas formed by water vapor is between 0.2 and 10 L / h / g (liters per hour per gram) of zeolitic support. Ionic exchange
• Said zeolite of MTW structural type that comprises the catalyst according to the invention is at least partly in acid form, ie in hydrogen form (H); the competing cation C being selected from the group consisting of the alkali or alkaline earth cations, preferably from the group consisting of Na + and K + cations, preferably the competitor cation C is the Na + cation.
• An ion exchange, preceded by calcination, may be carried out after step i) in the presence of ammonium nitrate or ammonium acetate at a concentration of 0.005 to 15 N, preferably 0.1 to 10 N at a temperature between 15 and 100 ° C for a period of 1 to 10 hours in a batch reactor or continuous.
• the zeolite obtained is dried, for example in an oven, at a temperature between room temperature and 250 ° C., before being calcined at a temperature of between 300 ° C. and 600 ° C. ° C under air. It is possible to proceed to successive exchanges.
• the exchange (s) can (s) be made (s) on the zeolite support after step ii).
• the shaping step (step ii)) is generally such that the catalyst is preferably in the form of extrudates or beads for use. In a variant of the catalyst preparation, shaping is carried out before calcination and ion exchange.
• any alumina known to those skilled in the art, of specific surface area and of variable pore volume is used, preferably a matrix chosen from clays, magnesia , aluminas, silicas, titanium oxide, boron oxide, zirconia, aluminum phosphates, titanium phosphates, zirconium phosphates and silicas aluminas. You can also use coal.
• the matrix is an alumina.
• the zeolite content in the support is between 1 and 20% by weight, preferably between 1 and 10% by weight.
• the preparation of the support according to said step ii) is advantageously followed by drying and then calcination.
• the drying is preferably carried out at a temperature between 100 and 150 ° C for a period of between 5 and 20 hours in an oven.
• the calcination is preferably carried out at a temperature between 250 ° C and 600 ° C for a period of between 1 and 8 hours.
• step iii) of preparing the catalyst comprising a zeolite of structural type MTW, preferably a ZSM-12 zeolite consists in depositing at least one metal of group VIII of the periodic table of elements and possibly at least one a metal selected from metals of groups NIA, IVA and VIIB.
• Said group VIII metal present in the catalyst according to the invention is chosen from iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum, preferably from metals noble and more preferably from palladium and platinum. Even more preferably, said group VIII metal is platinum. According to the method implemented for the deposition of said Group VIII metal, as indicated below in the description, said Group VIII metal, preferably platinum, can be deposited predominantly on the zeolite or on the matrix. .
• the metal selected from the metals of groups NIA, IVA and VI IB and possibly present in the catalyst according to the invention is chosen from gallium, indium, tin and rhenium, preferably from indium, tin and rhenium.
• the preparation of the catalyst according to the invention can be carried out by any method known to those skilled in the art.
• at least one metal VIII is introduced onto the support, namely either predominantly on the matrix, or predominantly on the zeolite or on the whole zeolite-matrix.
• Deposition of said metal on the support is advantageously carried out by the dry impregnation technique or the excess impregnation technique.
• All group VIII metal precursors are suitable for the deposition of one or more Group VIII metals (ux) on the support.
• any noble metal of group VIII it is possible to use ammonia compounds or compounds such as, for example, ammonium chloroplatinate, platinum dicarbonyl dichloride, hexahydroxyplatinic acid, palladium chloride or palladium nitrate. .
• Platinum is generally introduced in the form of hexachloroplatinic acid.
• the introduction of the Group VIII noble metal is preferably carried out by impregnation with an aqueous or organic solution of one of the metal compounds mentioned above.
• paraffinic, naphthenic or aromatic hydrocarbons containing, for example, from 6 to 12 carbon atoms per molecule
• halogenated organic compounds containing, for example, from 1 to 12 carbon atoms per molecule.
• Solvent mixtures can also be used.
• the control of certain parameters implemented during the deposition makes it possible to orient the deposition of the said metal (s) ( ux) mainly on the matrix or on the zeolite.
• the metal (s) of group VI II preferably platinum and / or palladium, predominantly on the matrix, anion exchange with hexachloroplatinic acid and / or hexachloropalladic acid, in the presence of a competing agent, for example hydrochloric acid, the deposit being generally followed by calcination, for example at a temperature of between 350 and 550 ° C. and for a period of between 1 and 4 hours.
• the group VIII metal (s) is (are) predominantly deposited on the matrix and the said metal (s) exhibit good dispersion and stability. good macroscopic distribution through the catalyst grain.
• the precursor may for example be chosen from:
• ammonia compounds such as tetrammine platinum (II) salts of formula Pt (NH 3 ) 4 X 2, hexammine platinum (IV) salts of formula Pt (NH 3 ) 6 X 4 ; platinum (IV) halogenopentammine salts of formula (PtX (NH 3) 5) X 3; N-tetrahalogenodiamine platinum salts of formula PtX4 (NH3) 2; and
• X being a halogen selected from the group consisting of chlorine, fluorine, bromine and iodine, X being preferably chlorine, and "acac" representing the acetylacetonate group (of formula C5H7O2), derived from acetylacetone .
• the group VIII metal (s) is (are) predominantly deposited on the zeolite and the said metal (s) have good dispersion and stability. good macroscopic distribution through the catalyst grain.
• the dry impregnation of the Group VIII metal on the support leads to the deposition of said metal on both the matrix and the zeolite.
• the catalyst according to the invention also contains at least one metal chosen from the metals of groups NIA, IVA and VIIB, all the deposition techniques such a metal known to those skilled in the art and all the precursors of such metals may be suitable.
• Group VIII metal (s) and NIA, IVA and VIIB group (s) may be added either separately or simultaneously in at least one unit step.
• at least one metal of groups NIA, IVA and VIIB is added separately, it is preferable that it be added after the Group VIII metal.
• the additional metal selected from the metals of groups NIA, IVA and VIIB may be introduced via compounds such as, for example, the chlorides, bromides and nitrates of the metals of groups NIA, IVA and VIIB.
• compounds such as, for example, the chlorides, bromides and nitrates of the metals of groups NIA, IVA and VIIB.
• indium, nitrate or chloride is advantageously used, and in the case of rhenium, perrhenic acid is advantageously used.
• tin chlorides SnCl 2 and SnCl 4 are preferred.
• the additional metal selected from the metals of the groups NIA, IVA and VIIB may also be introduced in the form of at least one organic compound chosen from the group consisting of the complexes of said metal, in particular the metal polyketone complexes and the hydrocarbyl metals.
• organometallic compound of said metal in an organic solvent.
• organohalogen compounds of the metal there may be mentioned in particular tetrabutyltin, in the case of tin, and triphenylindium, in the case of indium.
• the compound of the metal NIA, IVA and / or VIIB used is generally chosen from the group consisting of halide, nitrate , acetate, tartrate, carbonate and oxalate of the metal.
• the introduction is then advantageously carried out in aqueous solution. But it can also be introduced using a solution of an organometallic compound of the metal by for example, tetrabutyltin. In this case, before proceeding with the introduction of at least one metal of group VIII, calcination under air will be carried out.
• intermediate treatments such as, for example, calcination and / or reduction may be applied between the successive deposits of the different metals.
• the deposition of (s) metal (s) is followed by calcination, usually at a temperature between 250 ° C and 600 ° C, for a period of between 0.5 and 10 hours, preferably preceded by a drying, for example in an oven, at a temperature ranging from room temperature to 250 ° C, preferably from 40 ° C to 200 ° C. Said drying step is preferably conducted during the rise in temperature necessary to effect said calcination.
• Group VIII metal (s) preferably platinum, deposited on the zeolite and / or on the matrix, represents (s) from 0.01 to 2%, preferably from 0.05 to 1%, by weight relative to the weight of catalyst.
• the matrix is the 100% complement.
• said catalyst contains at least one metal selected from the metals of groups NIA, IVA and VIIB, the content thereof can be up to 2% by weight relative to the weight of catalyst. It is then advantageously from 0.01 to 2%, preferably from 0.05 to 1% by weight.
• the content thereof may be such that the ratio of the number of sulfur atoms to the number of group VIII metal atoms deposited is up to 2: 1. It is then advantageously from 0.5: 1 to 2: 1.
• said catalyst is subjected after step ii) or after step iii) to a treatment with water vapor so that its mesoporous volume is increased at least 10%, preferably at least 10.5% relative to its initial mesoporous volume, said initial mesoporous volume being generally between 0.55 and 0.75 ml / g.
• the increase in mesoporosity can be greater than 15% by weight.
• the treatment in the presence of steam to which the catalyst is subjected after step ii) or after step iii) is carried out under controlled conditions, namely: at a temperature between 300 and 400 ° C, preferably between 300 and 380 ° C, even more preferably between 330 and 370 ° C.
• the duration of said treatment is at least 0.5 hours, preferably between 0.5 hours and 24 hours, and more preferably between 1 hour and 12 hours.
• the partial pressure of water vapor during the treatment is advantageously between 0.01 and 0.07 MPa, preferably between 0.04 and 0.06 MPa.
• the water vapor is usually diluted in a neutral gas, oxygen or in air, preferably in air.
• the flow rate of water vapor gas is advantageously between 0.2 L / h / g and 10 L / h / g of zeolitic support.
• a reduction of the metal in hydrogen is advantageously carried out in situ before injection of the feedstock.
• the sulfur is introduced on the shaped catalyst, calcined, containing the metal or metals mentioned above, either in situ before the catalytic reaction, or ex situ. Possible sulphurisation occurs after the reduction.
• the reduction if the catalyst has not been reduced beforehand, occurs before the sulfurization.
• an ex situ sulphurization reduction is carried out and then sulphurization. The sulphurization is carried out in the presence of hydrogen using any sulphurizing agent well known to those skilled in the art, such as, for example, sulfur sulphide.
• the catalyst is treated with a dimethyl sulfide-containing filler in the presence of hydrogen, with a concentration such that the sulfur / metal atomic ratio is 1.5.
• the catalyst is then maintained for about 3 hours at about 400 ° C under hydrogen flow prior to feed injection.
• the isomerization process according to the invention consists in bringing into contact an aromatic section containing at least one aromatic compound having eight carbon atoms per molecule with at least said catalyst containing at least said MTW structural type zeolite, preferably said ZSM zeolite. -12, said catalyst having been prepared according to the implementation of each of said steps i), ii), iii) and iv) described above in the present description.
• the present invention also relates to a process for the isomerization of a filler in the presence of the catalyst according to the invention.
• the filler according to the invention is an aromatic cut containing at least one aromatic compound having eight carbon atoms per molecule and advantageously comprises either only a mixture of xylenes or only ethylbenzene or a mixture of xylene (s) and ethylbenzene.
• the isomerization process according to the invention comprises bringing said cup into contact with the catalyst according to the invention.
• a feed space velocity expressed in kilograms of feed introduced per kilogram of catalyst per hour, from 0.25 to 30 h -1 , preferably from 1 to 10 h -1 and more preferably from 2 to 6 h "1 .
• Example 1 (according to the invention) Preparation of the steam treated catalyst A at 350 ° C., containing zeolite ZSM-12 and 0.3% by weight of platinum.
• the raw material used is a synthetic ZSM-12 zeolite, comprising the organic structuring agent, silicon and aluminum, having an Si / Al atomic ratio equal to 60.
• This zeolite ZSM-12 is calcined at 550 ° C. under air flow for 6 hours.
• the calcined zeolite ZSM-12 is then shaped by extrusion with an alumina gel so as to obtain, after drying and calcination in dry air, a support consisting of extrudates of 1.4 mm in diameter, which contains by weight about 4% zeolite ZSM-12 and about 96% alumina.
• the mesoporous volume of the support is determined from the nitrogen adsorption isotherm and is 0.73 ml / g.
• the support thus obtained is subjected to anion exchange with hexachloroplatinic acid in the presence of a competing agent (hydrochloric acid), so as to deposit 0.3% by weight of platinum relative to the catalyst.
• the wet solid is then dried at 120 ° C for 12 hours and calcined in air at 500 ° C for one hour.
• the solid is then treated with steam at a partial pressure of 0.05 MPa in air at 2 L / hr / g at 350 ° C for 10 hours. After treatment, the The mesoporous volume of the catalyst is determined from the nitrogen adsorption isotherm and is 0.81 ml / g.
• the catalyst thus obtained contains, by weight, 4% of zeolite ZSM-12 partly in the hydrogen form (H), 95.7% of alumina and 0.3% of platinum.
• the platinum dispersion, measured by oxygen chemisorption, is about 80%.
• Example 2 Preparation of catalyst B without steam treatment containing zeolite ZSM-12 and 0.3% by weight of platinum.
• the raw material used is a synthetic ZSM-12 zeolite, comprising the organic structuring agent, silicon and aluminum, having an Si / Al atomic ratio equal to 60.
• This zeolite ZSM-12 is calcined at 550 ° C. under air flow for 6 hours.
• the calcined zeolite ZSM-12 is then shaped by extrusion with an alumina gel so as to obtain, after drying and calcination in dry air, a support consisting of extrudates of 1.4 mm in diameter, which contains by weight about 4% zeolite ZSM-12 and about 96% alumina.
• the mesoporous volume of the support is determined from the nitrogen adsorption isotherm and is 0.73 ml / g.
• the support thus obtained is subjected to anion exchange with hexachloroplatinic acid in the presence of a competing agent (hydrochloric acid), so as to deposit 0.3% by weight of platinum relative to the catalyst.
• a competing agent hydroochloric acid
• the wet solid is then dried at 120 ° C for 12 hours and calcined in air at 500 ° C for one hour.
• the catalyst thus obtained contains, by weight, 4% of zeolite ZSM-12 partly in the hydrogen form (H), 95.7% of alumina and 0.3% of platinum.
• the platinum dispersion, measured by oxygen chemisorption, is about 80%.
• Example 3 (Non-compliant): Preparation of steam-treated catalyst C at 550 ° C, containing zeolite ZSM-12 and 0.3 wt% platinum.
• the raw material used is a synthetic ZSM-12 zeolite, comprising the organic structuring agent, silicon and aluminum, having an Si / Al atomic ratio equal to 60.
• This zeolite ZSM-12 is calcined at 550 ° C. under air flow for 6 hours.
• the calcined zeolite ZSM-12 is then shaped by extrusion with an alumina gel so as to obtain, after drying and calcination in dry air, a support consisting of extrudates of 1.4 mm in diameter, which contains by weight about 4% zeolite ZSM-12 and about 96% alumina.
• the mesoporous volume of the support is determined from the nitrogen adsorption isotherm and is 0.73 ml / g.
• the support thus obtained is subjected to anion exchange with hexachloroplatinic acid in the presence of a competing agent (hydrochloric acid), so as to deposit 0.3% by weight of platinum relative to the catalyst.
• the wet solid is then dried at 120 ° C for 12 hours and calcined in air at 500 ° C for one hour.
• the solid is then treated with steam at a partial pressure of 0.09 MPa in air at 2 L / hr / g at 550 ° C for 10 hours.
• the mesoporous volume of the catalyst is determined from the nitrogen adsorption isotherm and is 0.75 ML / g.
• the catalyst thus obtained contains, by weight, 4% of zeolite ZSM-12 partly in the hydrogen form (H), 95.7% of alumina and 0.3% of platinum.
• the platinum dispersion, measured by oxygen chemisorption, is about 80%.
• the catalysts are maintained for 3 hours at 480 ° C. under a flow of pure hydrogen, and then the feedstock is injected.
• Catalysts A, B and C are contacted with the feed, the operating conditions are as follows:
• VVH space velocity
• the catalysts were compared in terms of activity (by the equilibrium approach of paraxylene and the conversion of ethylbenzene).
• AEQ pX (%) 100 X (% pX ef f uct " % pXcharge) / (% pXequilibrium " % pXcharge)
• % EBchar ge concentration of ethylbenzene initially present in the feed,% EB eff
• Uent concentration of ethylbenzene present in the effluent at the end of the reaction.
• the catalyst A treated with water vapor at 350 ° C. with a partial pressure of water of 0.05 MPa shows a significant gain in conversion of ethylbenzene as well as an activity in approach to the thermodynamic equilibrium of paraxylene. increased with respect to the catalysts which have not undergone steam treatment (catalyst B) and have undergone steam treatment at a temperature above 400 ° C. and at a partial water pressure of greater than 0.07 MPa (catalyst VS).

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