EP1890811A2 - Structure and catalytic filter for filtering a gas comprising a hydrophobic or oleophobic cement - Google Patents

Structure and catalytic filter for filtering a gas comprising a hydrophobic or oleophobic cement

Info

Publication number
EP1890811A2
EP1890811A2 EP06778932A EP06778932A EP1890811A2 EP 1890811 A2 EP1890811 A2 EP 1890811A2 EP 06778932 A EP06778932 A EP 06778932A EP 06778932 A EP06778932 A EP 06778932A EP 1890811 A2 EP1890811 A2 EP 1890811A2
Authority
EP
European Patent Office
Prior art keywords
cement
hydrophobic
filter
coating
catalyst
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP06778932A
Other languages
German (de)
French (fr)
Inventor
Patricia Andy
Anthony Briot
Sébastien BARDON
Caroline Tardivat
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Saint Gobain Centre de Recherche et dEtudes Europeen SAS
Original Assignee
Saint Gobain Centre de Recherche et dEtudes Europeen SAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Saint Gobain Centre de Recherche et dEtudes Europeen SAS filed Critical Saint Gobain Centre de Recherche et dEtudes Europeen SAS
Publication of EP1890811A2 publication Critical patent/EP1890811A2/en
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
    • F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
    • B01J35/56—Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional monoliths
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0215—Coating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/022—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
    • F01N3/0222—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous the structure being monolithic, e.g. honeycombs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/01—Engine exhaust gases
    • B01D2258/012—Diesel engines and lean burn gasoline engines
    • 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T156/00—Adhesive bonding and miscellaneous chemical manufacture
    • Y10T156/10—Methods of surface bonding and/or assembly therefor
    • Y10T156/1002—Methods of surface bonding and/or assembly therefor with permanent bending or reshaping or surface deformation of self sustaining lamina
    • Y10T156/1003—Methods of surface bonding and/or assembly therefor with permanent bending or reshaping or surface deformation of self sustaining lamina by separating laminae between spaced secured areas [e.g., honeycomb expanding]
    • 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
    • Y10T428/24149—Honeycomb-like

Definitions

  • the invention relates to the field of particulate filters especially used in an exhaust line of an engine for the removal of soot produced by the combustion of a diesel fuel in an internal combustion engine. More specifically, the invention relates to a filter structure and a particulate filter, said filter comprising a material conferring catalytic properties, and the method of preparation thereof.
  • Filtration structures for soot contained in the exhaust gas of an internal combustion engine are well known in the prior art. These structures most often have a honeycomb structure, one of the faces of the structure for the admission of the exhaust gases to be filtered and the other side the exhaust of the filtered exhaust gases.
  • the structure comprises, between the intake and discharge faces, a set of adjacent ducts or channels of axes parallel to each other separated by porous filtration walls, which ducts are closed to one or the other of their ends for delimiting input chambers s 'opening according to the inlet face and outlet chambers s' opening according to the discharge face.
  • the peripheral part of the structure is surrounded by a cement, called coating cement in the following description.
  • the channels are alternately closed in an order such that the exhaust gases, during the crossing of the honeycomb body, are forced to pass through the side walls input channels to join the output channels. In this way, the particles or soot are deposited and accumulate on the porous walls of the filter body.
  • the filter bodies are porous ceramic material, for example cordierite or silicon carbide.
  • the particulate filter is subjected to a succession of filtration (soot accumulation) and regeneration (soot elimination) phases.
  • filtration phases the soot particles emitted by the engine are retained and are deposited inside the filter.
  • regeneration phases the soot particles are burned inside the filter, in order to restore its filtration properties.
  • the porous structure is then subjected to intense thermal and mechanical stresses, which can cause micro-cracking likely over time to cause a severe loss of filtration capacity of the unit, or even its complete deactivation. This phenomenon is particularly observed on monolithic filters of large diameter.
  • the coefficients of thermal expansion of the different parts of the structure (that is to say the filtration elements, the coating cement, the joint cement, the cement constituting the plugs) must be of substantially the same order.
  • said parts are synthesized on the basis of the same material, most often silicon carbide SiC or cordierite. This choice also makes it possible to homogenize the distribution of heat during the regeneration of the filter.
  • the expression "at the base of the same material” is meant in the sense of the present description that the material consists of at least 25% by weight, preferably at least 45% by weight and very preferably at least 70% by weight of said material.
  • the filters or porous soot filtration structures as previously described are mainly used on a large scale in the exhaust gas pollution control devices of a diesel engine.
  • the exhaust line of the internal combustion engine comprises, in series, a catalytic purification member and a particulate filter.
  • the catalytic purification unit generally of open honeycomb structure, is suitable for the treatment of pollutants in the gas phase, whereas the Particle filter is suitable for removing soot particles emitted by the engine.
  • the succession of filter elements on the exhaust line is however responsible for a significant loss of load on said line, which may affect the engine performance .
  • the honeycomb structure is impregnated with a solution comprising the catalyst or a precursor of the catalyst.
  • Such methods generally include an immersion impregnation step in either a solution containing a catalyst precursor or a catalyst solubilized in water (or another polar solvent), or a suspension in water of catalytic particles.
  • a solution containing a catalyst precursor or a catalyst solubilized in water (or another polar solvent), or a suspension in water of catalytic particles An example of such a process is described in US Pat. No. 5,866,210.
  • the application at the other end of the filter of a vacuum allows in a second time the rise of the solution in the structure and consequently the coating of the internal walls of the honeycomb structure.
  • the impregnation step can be carried out using a solution containing a non-polar solvent such as an oil or a hydrocarbon or surfactants.
  • said impregnations can be obtained by pumping, by applying a vacuum or under the pressure of the liquid comprising the impregnation solution, on at least one end of the monolith.
  • the processes described are characterized by a combination of these different techniques, in successive steps, the final step allowing the removal of the excess solution in the filter by introduction of air under pressure or by suction.
  • One of the essential goals sought by the The use of these processes is to obtain a uniform coating of the catalyst on or even inside at least a portion of the porous walls of the channels constituting the internal part of the structure and through which the exhaust gases pass.
  • the cost of the deposited catalysts which most often contain precious metals of the Platinum group (Pt, Pd, Rh) on an oxide support represents a significant part of the overall cost of the impregnation process. It is therefore important not only that the catalyst be deposited uniformly on the walls of the filter channels, but also that a minimum part thereof is deposited on the parts of the honeycomb structure that do not play. a role of filtration of gases or soot. Said parts are essentially the coating cement for a monolithic structure, added cement joint and plugs, in the case of a filter block as previously described, that is to say combining several monolithic elements in a nest. 'bee.
  • Patent application JP 56-133036 discloses a method for depositing a catalyst on a ceramic honeycomb structure for depositing rare metals mainly in the walls of the filter channels. It consists, on a monolithic ceramic structure, to coat the coating cement, before the deposition of the catalyst, with a hydrophobic agent of the family of fluorinated or silicone compounds, the front and rear faces of the structure monolithic having been previously masked with an adhesive.
  • the joint cement surface may represent more than 10% of the area of the inlet (and outlet) section of the filter.
  • the cumulative area of the seals and plugs may represent more than 30% of the area of the filter inlet section.
  • the assembly process most often causes a relative irregularity of the filter according to the invention at its front and rear faces.
  • This non-flatness of the faces results from a misalignment of the elements, following the possible sliding of the elements relative to each other, both in a longitudinal and transverse direction, before the setting of the joint cement.
  • the masking of the elements itself becomes imprecise, difficult to reproducibly perform over a whole population of filters and can lead to undesired deposits of hydrophobic solution at the top of the inlet or outlet channels. evacuation and then hinder the homogeneous deposition of catalyst on the filtering parts.
  • the object of the present invention is therefore to limit, during an impregnation process of a particle filter having a structure assembled from honeycomb elements, the amount of catalyst present on the parts of structure that do not exert the filtration function of the gas to be filtered or soot. More specifically, the present invention relates in a first aspect to a usable structure, after deposition of a catalyst, for the filtration of a gas loaded with soot particles and pollutants in the gas phase, said structure comprising
  • a central part comprising a plurality of honeycomb filter elements interconnected by a joint cement, the one or more elements comprising a set of adjacent ducts or channels with axes parallel to one another separated by porous walls, which conduits being closed by plugs at one or the other of their ends to define inlet chambers opening on a gas inlet face and outlet chambers opening on a discharge face of gas, so that the gas to be filtered passes through the porous walls and
  • hydrophobic material in the sense of the present description any material for reducing the amount of a polar liquid, such as water, adsorbed on the surface or in the porosity of the cement used, when the structure is immersed in said polar liquid.
  • oleophobic material in the sense of the present description any material for reducing the amount of a non-polar liquid, such as an oil, adsorbed on the surface or in the porosity of the cement used, when the structure is immersed in said non-polar liquid.
  • said structure is constituted by a filter block associating several filtering elements monolithic honeycomb, said elements being bonded by a joint cement comprising a hydrophobic or oleophobic material.
  • said element or elements, the coating cement and possibly the joint cement and / or the cement constituting the plugs are based on the same ceramic material, preferably based on silicon carbide SiC.
  • Any material known for its hydrophobic or oleophobic action on the surface or in the porosity of a cement can be used according to the invention. Examples of such compounds are well known in the art. Examples will be given in the following description.
  • the invention also relates to a process for obtaining a filter for the filtration of a gas loaded with particles of soot and pollutants in the gas phase such as carbon monoxide CO, NOx nitrogen oxides, SOx sulfur oxides, HC hydrocarbons, said process comprising the steps of: manufacturing a first structure as previously described, in which the coating cement and preferably the joint cement and optionally the cement constituting the plugs comprise a hydrophobic material, impregnating said structure with a solution containing a precursor of the catalyst or the catalyst solubilized in a polar solvent such as water, or a suspension of catalytic particles in a polar solvent such as water.
  • a polar solvent such as water
  • a first class of hydrophobic materials that can be used according to the invention is in the form of a powder, for example graphite carbon, CaF2, or other hydrophobic mineral powders containing the fluorine element.
  • the hydrophobic material preferably has a suitable particle size, for example in the form of a powder of which 90% cumulated mass of grains have a diameter of less than 500 microns and preferably 90% by mass of the grains have a diameter of less than 200 microns.
  • the ceramist will adapt the granulometric spectrum of SiC according to the invention to the incorporation of the hydrophobic material or will make appropriate additions, in particular of plasticizer.
  • hydrophobic materials that may be used according to the invention are organic or organometallic compounds chosen from those known for their water-repellent action in the field of cementitious materials for construction, for example of the type described in the reference work "Lea's Chemistry of Cernent and Concrete, 4th ed., PC Hewlett, 1988, p883-887.
  • Such compounds are, for example, metal salts of C12-C20 fatty acids such as alkali or alkaline earth stearates or oleates, silicones, silanes, siloxanes, siliconates and organofluorinated compounds of low surface tension whose PTFE powders, acrylic and vinyl resins, paraffinic oils.
  • the material may be incorporated into the formulation of the coating cement and / or seal and / or the cement constituting the plugs before the steps coating and assembly of the structure as described in Example 2, or deposited by liquid or gaseous manner after said steps of coating / assembly of the structure as described in Example 3.
  • the mode according to the invention in which the hydrophobe or oleophobe is incorporated into the cement formulation (and is therefore ultimately present in the mass of said cement and / or forms part of it) has the advantage of not no need for additional step with respect to the method of manufacturing the filter incorporating a process of deposition of hydrophobic or oleophobic gas or liquid.
  • the masking step for selectively depositing it in the porosity of the coating cement and / or seal and / or plugs is not necessary.
  • the embodiment by incorporation can most often be carried out only in limited proportions of hydrophobic or oleophobic, typically between 0.1 and 10%, preferably between 0.5 and 6% by weight relative to the dry mass cement, depending on the nature of the addition, the granulometry of the graphite powder, for example, or the hydrophobicity, especially the wetting angle with water. Below 0.1%, it has been observed that the hydrophobic effect is insufficient. Beyond 10% the addition of water required for the implementation of the cement is too high, which leads to problems of cracking during the drying of the cement and then the mechanical cohesion of the assembled filter. Beyond 10% may also arise problems of dispersion of the incorporated addition questioning the homogeneity of the cement and the desired effect. Caking or hardening problems can also arise for too high additions, see foaming problems, which are not soluble with anti-foaming agents.
  • the hydrophobe or oleophobe is deposited by gaseous route, it is possible, for example and as described in Example 3, to vaporize it at low temperature and then redeposit it on the surface of the cement, advantageously only on unmasked parts of the filter.
  • the process for obtaining the filter comprises steps of: manufacturing a first structure as previously described, in which the coating cement, preferably the joint cement and possibly the cement constituting the plugs; comprise an oleophobic material, impregnating said structure with a solution containing a precursor of the catalyst or the catalyst solubilized in a hydrophobic solvent such as a hydrocarbon or an oil, or a suspension of catalytic particles in a solution containing a non-polar solvent such as an oil or a hydrocarbon or surfactants.
  • the oleophobic material is for example included in the group consisting of silanes, siloxanes, siliconates, organofluorinated compounds of low surface tension.
  • the oleophobic material is, for example, a fluorinated polymer or a silane derivative, or a mixture of silane and fluorosilane such as Z-6707 silane® from Dow Corning, or a fluoropolymer such as Zonyl MP 1400® from Du Pont Germany, in the form of a powder with a median diameter of particles of about 12 microns.
  • the products which are suitable are those having a critical surface tension lower than the surface tension of the solution in which the catalyst is solubilized.
  • the incorporation of the oleophobic material can be done according to the same principles and techniques as previously described for the incorporation of the hydrophobic material.
  • said impregnation of the structure with the polar or nonpolar liquid containing the catalyst or a precursor of the catalyst can be carried out by any method known in the art and in particular by pumping the solution through the structure, by applying a vacuum or a vacuum or under the pressure of the liquid comprising the impregnating solution on at least one end of the structure.
  • a vacuum or a vacuum or under the pressure of the liquid comprising the impregnating solution on at least one end of the structure.
  • the impregnation step may be implemented according to the methods and / or devices known from the prior art and in particular according to one of the methods or devices described in the patents or patent applications mentioned above.
  • the invention relates to the catalytic filter obtained by the manufacturing method as just described and which is characterized by the presence of a hydrophobic or oleophobic material on the surface and preferably in porosity. coating and / or joint cement, as well as by the presence of a minimal amount of catalyst on said cement.
  • a minor amount is understood to mean a smaller amount of catalyst relative to the amount of catalyst present in the filtering walls of the catalyst. filter, that is to say within the monolithic elements in honeycomb.
  • a filtering structure comprising an assembly of filter elements made of silicon carbide bonded with a joint cement was synthesized according to the techniques described in the patent
  • a cement for the joint and the coating is then prepared by mixing:
  • a quantity of water corresponding to 10% of the weight of this mixture is added to obtain a cement of adequate viscosity.
  • This crude structure is then immersed in a bath of an aqueous solution containing the appropriate proportions of a platinum precursor in the form of H 2 PtClO, and a precursor of cerium oxide CeO 2 (in the nitrate form of cerium) and a precursor of zirconium oxide ZrO 2 (in the form of zirconyl nitrate) according to the principles described in the publication EP 1 338 322 A1.
  • the filter is impregnated with the solution according to an implementation mode. similar to that described in US Patent 5,866,210.
  • the filter is then dried at about 150 ° C. and then heated to a temperature of about 600 ° C.
  • a catalytic filter was manufactured by repeating the same steps as those of Example 1, with the difference that this time the cement formulation was modified as follows by incorporating a hydrophobic graphite powder:
  • a temporary binder and a plasticizer of the Cellulose type 0.1% by weight of a deflocculant of the TPPNa type (sodium tripolyphosphate).
  • a quantity of water corresponding to approximately 15% of the weight of this mixture is added to obtain a cement of adequate viscosity.
  • the chemical analysis shows a total concentration of Pt 49 g / ft 3 , or 4.3 grams distributed over the different parts of the filter.
  • a catalytic filter was manufactured by repeating the same steps as those of Example 1.
  • Masks are then applied to the parts of the filter on which it is not desired to deposit the hydrophobic agent, that is to say the parts other than the apparent cement joints between elements and the filter coating cement.
  • the masks were carefully cut and placed manually, because of the irregularities of the front and back surfaces of the filter, inherent to the assembly process of the elements.
  • the masked filter is then placed in a desiccator on a support plate. About 0.5 ml of perfluorodecyltrichlorosilane is deposited on the bottom of the desiccator by filter.
  • the chemical analysis shows a total concentration of Pt of 48 g / ft 3 , ie 4.2 grams distributed over the different parts of the filter.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Filtering Materials (AREA)
  • Catalysts (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Filtering Of Dispersed Particles In Gases (AREA)

Abstract

The invention concerns an assembled structure useable, after depositing a catalyst, for filtering a gas loaded with soot particles and gaseous pollutants wherein cement is used as coating and/or as joint comprising at least superficially a hydrophobic or oleophobic material. The invention also concerns an assembled catalytic filter obtained after impregnating in a catalytic solution said structure as well as a method for making the filter from said structure.

Description

STRUCTURE ET FILTRE CATALYTIQUE POUR LA FILTRATION D'UN GAZ COMPRENANT UN CIMENT HYDROPHOBE OU OLEOPHOBE STRUCTURE AND CATALYTIC FILTER FOR FILTERING GAS COMPRISING HYDROPHOBIC OR OLEOPHOBIC CEMENT
L'invention se rapporte au domaine des filtres à particules notamment utilisés dans une ligne d'échappement d'un moteur pour l'élimination des suies produites par la combustion d'un carburant diesel dans un moteur à combustion interne. Plus précisément, l'invention porte sur une structure pour filtre et sur un filtre à particules, ledit filtre comprenant un matériau lui conférant des propriétés catalytiques, ainsi qu'au procédé de préparation de celui-ci.The invention relates to the field of particulate filters especially used in an exhaust line of an engine for the removal of soot produced by the combustion of a diesel fuel in an internal combustion engine. More specifically, the invention relates to a filter structure and a particulate filter, said filter comprising a material conferring catalytic properties, and the method of preparation thereof.
Les structures de filtration pour les suies contenues dans les gaz d'échappement de moteur à combustion interne sont bien connues de l'art antérieur. Ces structures présentent le plus souvent une structure en nid d'abeille, une des faces de la structure permettant l'admission des gaz d'échappement à filtrer et l'autre face l'évacuation des gaz d'échappement filtrés. La structure comporte, entre les faces d'admission et d'évacuation, un ensemble de conduits ou canaux adjacents d'axes parallèles entre eux séparés par des parois poreuses de filtration, lesquels conduits sont obturés à l'une ou l'autre de leurs extrémités pour délimiter des chambres d'entrée s ' ouvrant suivant la face d'admission et des chambres de sortie s 'ouvrant suivant la face d'évacuation. Pour une bonne étanchéité, la partie périphérique de la structure est entourée d'un ciment, appelé ciment de revêtement dans la suite de la description. Les canaux sont alternativement obturés dans un ordre tel que les gaz d'échappement, au cours de la traversée du corps en nid d'abeille, sont contraints de traverser les parois latérales des canaux d'entrée pour rejoindre les canaux de sortie. De cette manière, les particules ou suies se déposent et s'accumulent sur les parois poreuses du corps filtrant. Le plus souvent, les corps filtrants sont en matière céramique poreuse, par exemple en cordiérite ou en carbure de silicium.Filtration structures for soot contained in the exhaust gas of an internal combustion engine are well known in the prior art. These structures most often have a honeycomb structure, one of the faces of the structure for the admission of the exhaust gases to be filtered and the other side the exhaust of the filtered exhaust gases. The structure comprises, between the intake and discharge faces, a set of adjacent ducts or channels of axes parallel to each other separated by porous filtration walls, which ducts are closed to one or the other of their ends for delimiting input chambers s 'opening according to the inlet face and outlet chambers s' opening according to the discharge face. For a good seal, the peripheral part of the structure is surrounded by a cement, called coating cement in the following description. The channels are alternately closed in an order such that the exhaust gases, during the crossing of the honeycomb body, are forced to pass through the side walls input channels to join the output channels. In this way, the particles or soot are deposited and accumulate on the porous walls of the filter body. Most often, the filter bodies are porous ceramic material, for example cordierite or silicon carbide.
De façon connue, durant son utilisation, le filtre à particules est soumis à une succession de phases de filtration (accumulation des suies) et de régénération (élimination des suies) . Lors des phases de filtration, les particules de suies émises par le moteur sont retenues et se déposent à l'intérieur du filtre. Lors des phases de régénération, les particules de suie sont brûlées à l'intérieur du filtre, afin de lui restituer ses propriétés de filtration. La structure poreuse est alors soumise à des contraintes thermiques et mécaniques intenses, qui peuvent entraîner des micro-fissurations susceptibles sur la durée d'entraîner une perte sévère des capacités de filtration de l'unité, voire sa désactivation complète. Ce phénomène est particulièrement observé sur des filtres monolithiques de grand diamètre.In known manner, during use, the particulate filter is subjected to a succession of filtration (soot accumulation) and regeneration (soot elimination) phases. During the filtration phases, the soot particles emitted by the engine are retained and are deposited inside the filter. During the regeneration phases, the soot particles are burned inside the filter, in order to restore its filtration properties. The porous structure is then subjected to intense thermal and mechanical stresses, which can cause micro-cracking likely over time to cause a severe loss of filtration capacity of the unit, or even its complete deactivation. This phenomenon is particularly observed on monolithic filters of large diameter.
Pour résoudre ces problèmes et augmenter la durée de vie des filtres, il a été proposé plus récemment des structures de filtration plus complexes, associant en un bloc filtrant plusieurs éléments monolithiques en nid d'abeille. Les éléments, après bouchage afin de délimiter les chambres d'entrée et les chambres de sortie du gaz, sont le plus souvent assemblés entre eux par collage au moyen d'un ciment de nature céramique, appelé dans la suite de la description ciment de joint ou joint. Des exemples de telles structures filtrantes sont par exemple décrites dans les demandes de brevets EP 816 065, EP 1 142 619, EP 1 455 923 ou encore WO 2004/090294. II est connu que dans ce type de structure, afin d'assurer une meilleure relaxation des contraintes, les coefficients de dilatation thermique des différentes parties de la structure (c'est-à-dire les éléments de filtration, le ciment de revêtement, le ciment de joint, le ciment constituant les bouchons) doivent être sensiblement du même ordre. De ce fait, lesdites parties sont synthétisées sur la base d'un même matériau, le plus souvent le carbure de silicium SiC ou la cordiérite. Ce choix permet en outre d'homogénéiser la répartition de la chaleur lors de la régénération du filtre. Par l'expression « à la base d'un même matériau », on entend au sens de la présente description que le matériau est constitué d'au moins 25% poids, de préférence d'au moins 45% poids et de manière très préférée d'au moins 70% poids dudit matériau.To solve these problems and increase the life of the filters, it has been proposed more recently more complex filtration structures, combining in a filter block several monolithic elements in honeycomb. The elements, after plugging in order to delimit the inlet chambers and the gas outlet chambers, are most often assembled together by bonding by means of a cement of a ceramic nature, hereinafter referred to as cement jointing. or attached. Examples of such filter structures are for example described in patent applications EP 816 065, EP 1 142 619, EP 1 455 923 or WO 2004/090294. It is known that in this type of structure, in order to ensure a better relaxation of the stresses, the coefficients of thermal expansion of the different parts of the structure (that is to say the filtration elements, the coating cement, the joint cement, the cement constituting the plugs) must be of substantially the same order. As a result, said parts are synthesized on the basis of the same material, most often silicon carbide SiC or cordierite. This choice also makes it possible to homogenize the distribution of heat during the regeneration of the filter. By the expression "at the base of the same material" is meant in the sense of the present description that the material consists of at least 25% by weight, preferably at least 45% by weight and very preferably at least 70% by weight of said material.
Les filtres ou structures de filtration poreuses des suies tels que précédemment décrites sont principalement utilisés à grande échelle dans les dispositifs de dépollution des gaz d'échappement d'un moteur thermique diesel.The filters or porous soot filtration structures as previously described are mainly used on a large scale in the exhaust gas pollution control devices of a diesel engine.
En plus du problème de traitement des suies, la transformation des émissions polluantes en phase gazeuse (c'est à dire principalement les oxydes d'azote (NOx) ou de soufre (SOx) et le monoxyde de carbone (CO) , voire les hydrocarbures imbrûlés) en des gaz moins nocifs (tels que l'azote gazeux (N2) ou le dioxyde de carbone (CO2)) nécessite un traitement catalytique supplémentaire.In addition to the soot treatment problem, the transformation of polluting emissions into the gas phase (ie mainly nitrogen oxides (NO x ) or sulfur (SO x ) and carbon monoxide (CO), or even unburned hydrocarbons) to less harmful gases (such as nitrogen gas (N 2 ) or carbon dioxide (CO 2 )) requires additional catalytic treatment.
Selon une première technologie, pour éliminer tous les polluants, la ligne d'échappement du moteur à combustion interne comprend, en série, un organe de purification catalytique et un filtre à particules .According to a first technology, to eliminate all pollutants, the exhaust line of the internal combustion engine comprises, in series, a catalytic purification member and a particulate filter.
L'organe de purification catalytique, généralement de structure en nid d'abeille ouverte, est adapté pour le traitement des polluants en phase gazeuse, alors que le filtre à particules est adapté pour éliminer les particules de suies émises par le moteur. Outre la complexité de la mise en œuvre de cette solution et son coût, la succession des éléments filtrants sur la ligne d'échappement est cependant responsable d'une perte de charge non négligeable sur ladite ligne, susceptible d'influer sur les performances du moteur.The catalytic purification unit, generally of open honeycomb structure, is suitable for the treatment of pollutants in the gas phase, whereas the Particle filter is suitable for removing soot particles emitted by the engine. In addition to the complexity of the implementation of this solution and its cost, the succession of filter elements on the exhaust line is however responsible for a significant loss of load on said line, which may affect the engine performance .
Pour résoudre ces problèmes, on a cherché à transférer la fonction catalytique sur un filtre à particules du type monolithe. Selon les procédés classiquement utilisés, la structure en nid d'abeille est imprégnée par une solution comprenant le catalyseur ou un précurseur du catalyseur.To solve these problems, it was sought to transfer the catalytic function on a particle filter of the monolithic type. According to the conventionally used methods, the honeycomb structure is impregnated with a solution comprising the catalyst or a precursor of the catalyst.
De tels procédés comportent en général une étape d'imprégnation par immersion soit dans une solution contenant un précurseur du catalyseur ou le catalyseur solubilisé dans l'eau (ou un autre solvant polaire), soit une suspension dans l'eau de particules catalytiques . Un exemple d'un tel procédé est décrit par le brevet US 5,866,210. Selon ce procédé, l'application à l'autre extrémité du filtre d'une dépression permet dans un deuxième temps la montée de la solution dans la structure et par suite le revêtement des parois internes de la structure en nid d'abeille. Alternativement mais plus rarement, l'étape d'imprégnation peut être réalisée en utilisant une solution contenant un solvant non polaire tels qu'une huile ou un hydrocarbure ou des tensioactifs .Such methods generally include an immersion impregnation step in either a solution containing a catalyst precursor or a catalyst solubilized in water (or another polar solvent), or a suspension in water of catalytic particles. An example of such a process is described in US Pat. No. 5,866,210. According to this method, the application at the other end of the filter of a vacuum allows in a second time the rise of the solution in the structure and consequently the coating of the internal walls of the honeycomb structure. Alternatively, but more rarely, the impregnation step can be carried out using a solution containing a non-polar solvent such as an oil or a hydrocarbon or surfactants.
Selon d'autres réalisations du procédé d'imprégnation des filtres en nid d'abeille, lesdites imprégnations peuvent être obtenues par pompage, par application d'un vide ou sous la pression du liquide comprenant la solution d'imprégnation, sur au moins une extrémité du monolithe. Le plus souvent les procédés décrits se caractérisent par une combinaison de ces différentes techniques, au cours d'étapes successives, l'étape finale permettant l'élimination de la solution en excès dans le filtre par introduction d'air sous pression ou par aspiration. Un des buts essentiels recherché par la mise en œuvre de ces procédés est l'obtention d'un revêtement uniforme du catalyseur sur, voire à l'intérieur d'au moins une partie des parois poreuses des canaux composant la partie interne de la structure et traversées par les gaz d' échappement .According to other embodiments of the process for impregnating the honeycomb filters, said impregnations can be obtained by pumping, by applying a vacuum or under the pressure of the liquid comprising the impregnation solution, on at least one end of the monolith. Most often the processes described are characterized by a combination of these different techniques, in successive steps, the final step allowing the removal of the excess solution in the filter by introduction of air under pressure or by suction. One of the essential goals sought by the The use of these processes is to obtain a uniform coating of the catalyst on or even inside at least a portion of the porous walls of the channels constituting the internal part of the structure and through which the exhaust gases pass.
De tels procédés, ainsi que les dispositifs pour leur mise en œuvre, sont par exemple décrits dans les demandes de brevets ou brevets US 2003/044520, WO 2004/091786, US 6,149,973, US 6,627,257, US 6,478,874, US 5,866,210, US 4,609,563, US 4,550,034, US 6,599,570, US 4,208,454 ou encore US 5,422,138.Such methods, as well as the devices for their implementation, are for example described in the patent applications or patents US 2003/044520, WO 2004/091786, US 6,149,973, US 6,627,257, US 6,478,874, US 5,866,210, US 4,609,563, US 4,550,034, US 6,599,570, US 4,208,454 or US 5,422,138.
Quelle que soit la méthode utilisée, le coût des catalyseurs déposés, qui contiennent le plus souvent des métaux précieux du groupe du Platine (Pt, Pd, Rh) sur un support oxyde représente une part non négligeable du coût global du procédé d'imprégnation. Il est donc important non seulement que le catalyseur soit déposé de manière uniforme sur les parois des canaux de filtration, mais également qu'une partie minimale de celui-ci se dépose sur les parties de la structure en nid d'abeille qui ne jouent pas un rôle de filtration des gaz ou des suies . Lesdites parties sont pour l'essentiel le ciment de revêtement pour une structure monolithique, additionné du ciment de joint et des bouchons, dans le cas d'un bloc filtrant tel que précédemment décrit, c'est à dire associant plusieurs éléments monolithiques en nid d'abeille.Whatever the method used, the cost of the deposited catalysts, which most often contain precious metals of the Platinum group (Pt, Pd, Rh) on an oxide support represents a significant part of the overall cost of the impregnation process. It is therefore important not only that the catalyst be deposited uniformly on the walls of the filter channels, but also that a minimum part thereof is deposited on the parts of the honeycomb structure that do not play. a role of filtration of gases or soot. Said parts are essentially the coating cement for a monolithic structure, added cement joint and plugs, in the case of a filter block as previously described, that is to say combining several monolithic elements in a nest. 'bee.
On connaît de la demande de brevet JP 56-133036 une méthode de dépôt de catalyseur sur une structure céramique en nid d'abeille visant à déposer les métaux rares principalement dans les parois des canaux de filtration. Elle consiste, sur une structure céramique monolithique, à revêtir le ciment de revêtement, avant le dépôt du catalyseur, d'un agent hydrophobe de la famille des composés fluorés ou siliconés, les faces avant et arrière de la structure monolithique ayant été préalablement masquées avec un adhésif.Patent application JP 56-133036 discloses a method for depositing a catalyst on a ceramic honeycomb structure for depositing rare metals mainly in the walls of the filter channels. It consists, on a monolithic ceramic structure, to coat the coating cement, before the deposition of the catalyst, with a hydrophobic agent of the family of fluorinated or silicone compounds, the front and rear faces of the structure monolithic having been previously masked with an adhesive.
Cette méthode ne peut cependant être utilisée efficacement pour minimiser la part de catalyseur se retrouvant sur le ciment de joint et les bouchons des éléments d'un filtre assemblé selon l'invention. A titre d'exemple, dans une telle structure, la surface de ciment de joint peut représenter plus de 10% de la surface de la section d'entrée (et de sortie) du filtre. Toujours à titre d'exemple et dans une telle structure, la surface cumulée des joints et des bouchons peut représenter plus de 30% de la surface de la section d'entrée du filtre.This method can however be used effectively to minimize the share of catalyst found on the joint cement and the plugs of the elements of an assembled filter according to the invention. By way of example, in such a structure, the joint cement surface may represent more than 10% of the area of the inlet (and outlet) section of the filter. Still as an example and in such a structure, the cumulative area of the seals and plugs may represent more than 30% of the area of the filter inlet section.
En outre, à la différence de la structure monolithique décrite dans JP 56-133036, le procédé d'assemblage entraine le plus souvent une relative irrégularité du filtre selon l'invention au niveau de ses faces avant et arrière. Cette non-planéité des faces résulte d'un défaut d'alignement des éléments, suite au possible glissement des éléments les uns par rapport aux autres, aussi bien dans un sens longitudinal que transversal, avant la prise du ciment de joint. Pour cette raison, le masquage des éléments devient lui-même imprécis, difficile à réaliser de façon reproductible sur toute une population de filtres et peut conduire à des dépôts non souhaités de solution à base d'hydrophobe au sommet des canaux d'admission ou d'évacuation et gêner ensuite le dépôt homogène de catalyseur sur les parties filtrantes .In addition, unlike the monolithic structure described in JP 56-133036, the assembly process most often causes a relative irregularity of the filter according to the invention at its front and rear faces. This non-flatness of the faces results from a misalignment of the elements, following the possible sliding of the elements relative to each other, both in a longitudinal and transverse direction, before the setting of the joint cement. For this reason, the masking of the elements itself becomes imprecise, difficult to reproducibly perform over a whole population of filters and can lead to undesired deposits of hydrophobic solution at the top of the inlet or outlet channels. evacuation and then hinder the homogeneous deposition of catalyst on the filtering parts.
L'objet de la présente invention est donc de limiter, lors d'un procédé d'imprégnation d'un filtre à particules présentant une structure assemblée à partir d'éléments en nid d'abeille, la quantité de catalyseur présente sur les parties de structure qui n'exercent pas la fonction de filtration du gaz à filtrer ou des suies . Plus précisément, la présente invention se rapporte selon un premier aspect à une structure utilisable, après dépôt d'un catalyseur, pour la filtration d'un gaz chargé en particules de suies et de polluants en phase gazeuse, ladite structure comprenantThe object of the present invention is therefore to limit, during an impregnation process of a particle filter having a structure assembled from honeycomb elements, the amount of catalyst present on the parts of structure that do not exert the filtration function of the gas to be filtered or soot. More specifically, the present invention relates in a first aspect to a usable structure, after deposition of a catalyst, for the filtration of a gas loaded with soot particles and pollutants in the gas phase, said structure comprising
- une partie centrale comprenant une pluralité d'éléments filtrants en nid d'abeille reliés entre eux par un ciment de joint, le ou lesdits éléments comprenant un ensemble de conduits ou canaux adjacents d'axes parallèles entre eux séparés par des parois poreuses, lesquels conduits étant obturés par des bouchons à l'une ou l'autre de leurs extrémités pour délimiter des chambres d'entrée s ' ouvrant suivant une face d'admission des gaz et des chambres de sortie s ' ouvrant suivant une face d'évacuation des gaz, de telle façon que le gaz à filtrer traverse les parois poreuses eta central part comprising a plurality of honeycomb filter elements interconnected by a joint cement, the one or more elements comprising a set of adjacent ducts or channels with axes parallel to one another separated by porous walls, which conduits being closed by plugs at one or the other of their ends to define inlet chambers opening on a gas inlet face and outlet chambers opening on a discharge face of gas, so that the gas to be filtered passes through the porous walls and
- une partie périphérique constituée par un ciment de revêtement protégeant lesdits éléments, ladite structure se caractérisant en ce que le ciment de revêtement, de préférence le ciment de joint et éventuellement le ciment constituant les bouchons, comprennent un matériau hydrophobe et/ou oléophobe.- A peripheral portion constituted by a coating cement protecting said elements, said structure being characterized in that the coating cement, preferably the joint cement and optionally the cement constituting the plugs, comprise a hydrophobic material and / or oleophobic.
Par matériau hydrophobe, on entend au sens de la présente description tout matériau permettant de réduire la quantité d'un liquide polaire, tel que l'eau, adsorbée à la surface ou dans la porosité du ciment utilisé, lorsque la structure est immergée dans ledit liquide polaire.By hydrophobic material is meant in the sense of the present description any material for reducing the amount of a polar liquid, such as water, adsorbed on the surface or in the porosity of the cement used, when the structure is immersed in said polar liquid.
Par matériau oléophobe, on entend au sens de la présente description tout matériau permettant de réduire la quantité d'un liquide non polaire, tel qu'une huile, adsorbée à la surface ou dans la porosité du ciment utilisé, lorsque la structure est immergée dans ledit liquide non polaire.By oleophobic material is meant in the sense of the present description any material for reducing the amount of a non-polar liquid, such as an oil, adsorbed on the surface or in the porosity of the cement used, when the structure is immersed in said non-polar liquid.
De préférence, ladite structure est constituée par un bloc filtrant associant plusieurs éléments filtrants monolithiques en nid d'abeille, lesdits éléments étant collés par un ciment de joint comprenant un matériau hydrophobe ou oléophobe .Preferably, said structure is constituted by a filter block associating several filtering elements monolithic honeycomb, said elements being bonded by a joint cement comprising a hydrophobic or oleophobic material.
Typiquement, le ou lesdits éléments, le ciment de revêtement et éventuellement le ciment de joint et/ou le ciment constituant les bouchons sont à base d'un même matériau céramique, préférentiellement à base de carbure de silicium SiC.Typically, said element or elements, the coating cement and possibly the joint cement and / or the cement constituting the plugs are based on the same ceramic material, preferably based on silicon carbide SiC.
Tout matériau connu pour son action hydrophobe ou oléophobe en surface ou dans la porosité d'un ciment peut être utilisé selon l'invention. Des exemples de tels composés sont bien connus de l'art antérieur. Des exemples seront donnés dans la suite de la description.Any material known for its hydrophobic or oleophobic action on the surface or in the porosity of a cement can be used according to the invention. Examples of such compounds are well known in the art. Examples will be given in the following description.
L'invention se rapporte également à un procédé d'obtention d'un filtre pour la filtration d'un gaz chargé en particules de suies et de polluants en phase gazeuse tel que l'oxyde de carbone CO, les oxydes d'azote NOx, les oxydes de soufre SOx, les hydrocarbures HC, ledit procédé comprenant les étapes : de fabrication d'une première structure telle que précédemment décrite, dans laquelle le ciment de revêtement et de préférence le ciment de joint et éventuellement le ciment constituant les bouchons comprennent un matériau hydrophobe, d' imprégnation de ladite structure par une solution contenant un précurseur du catalyseur ou le catalyseur solubilisé dans un solvant polaire tel que l'eau, soit une suspension de particules catalytiques dans un solvant polaire tel que l'eau.The invention also relates to a process for obtaining a filter for the filtration of a gas loaded with particles of soot and pollutants in the gas phase such as carbon monoxide CO, NOx nitrogen oxides, SOx sulfur oxides, HC hydrocarbons, said process comprising the steps of: manufacturing a first structure as previously described, in which the coating cement and preferably the joint cement and optionally the cement constituting the plugs comprise a hydrophobic material, impregnating said structure with a solution containing a precursor of the catalyst or the catalyst solubilized in a polar solvent such as water, or a suspension of catalytic particles in a polar solvent such as water.
Comme il sera montré par la suite dans les exemples fournis, un tel procédé permet de minimiser la quantité de métal précieux utilisée lors de l'étape d'imprégnation de la structure . Une première classe de matériaux hydrophobes utilisables selon l'invention se présente sous forme de poudre, par exemple le carbone graphite, le CaF2, ou d'autres poudres minérales hydrophobes contenant l'élément fluor. Le matériau hydrophobe présente de préférence une granulométrie adaptée, par exemple sous la forme d'une poudre dont 90% massique cumulé des grains présentent un diamètre inférieur à 500 microns et de préférence 90% massique des grains présentent un diamètre inférieur à 200 microns. De manière à optimiser la rhéologie et la compaction du ciment, si nécessaire et selon des techniques connues de l'art, le céramiste adaptera selon l'invention le spectre granulométrique de SiC à l'incorporation du matériau hydrophobe ou effectuera des ajouts adéquates, notamment de plastifiant.As will be shown later in the examples provided, such a method can minimize the amount of precious metal used during the step of impregnating the structure. A first class of hydrophobic materials that can be used according to the invention is in the form of a powder, for example graphite carbon, CaF2, or other hydrophobic mineral powders containing the fluorine element. The hydrophobic material preferably has a suitable particle size, for example in the form of a powder of which 90% cumulated mass of grains have a diameter of less than 500 microns and preferably 90% by mass of the grains have a diameter of less than 200 microns. In order to optimize the rheology and the compaction of the cement, if necessary and according to techniques known in the art, the ceramist will adapt the granulometric spectrum of SiC according to the invention to the incorporation of the hydrophobic material or will make appropriate additions, in particular of plasticizer.
Une autre classe de matériaux hydrophobes utilisables selon l'invention sont des composés organiques ou organométalliques choisis parmi ceux connus pour leur action hydrofuge dans le domaine des matériaux cimentaires pour la construction, par exemple du type décrit dans l'ouvrage de référence « Lea's Chemistry of Cernent and Concret, 4th ed, P.C. Hewlett, 1988, p883-887 ».Another class of hydrophobic materials that may be used according to the invention are organic or organometallic compounds chosen from those known for their water-repellent action in the field of cementitious materials for construction, for example of the type described in the reference work "Lea's Chemistry of Cernent and Concrete, 4th ed., PC Hewlett, 1988, p883-887.
De tels composés sont par exemple des sels métalliques d'acides gras C12-C20 comme les stéarates ou les oléates d'alcalins ou d' alcalino-terreux, les silicones, les silanes, siloxanes, siliconates, les composés organofluorés de faible tension superficielle dont les poudres de PTFE, les résines acryliques et vinyliques, les huiles paraffiniques . Selon l'invention, plusieurs modes d'incorporation du matériau, suivant sa nature, sont possibles: le matériau peut-être soit incorporé à la formulation du ciment de revêtement et/ou de joint et/ou du ciment constituant les bouchons avant les étapes de revêtement et d'assemblage de la structure comme cela est décrit dans l'exemple 2, soit déposé par voie liquide ou gazeuse après lesdites étapes de revêtement/assemblage de la structure comme décrit dans l'exemple 3.Such compounds are, for example, metal salts of C12-C20 fatty acids such as alkali or alkaline earth stearates or oleates, silicones, silanes, siloxanes, siliconates and organofluorinated compounds of low surface tension whose PTFE powders, acrylic and vinyl resins, paraffinic oils. According to the invention, several modes of incorporation of the material, depending on its nature, are possible: the material may be incorporated into the formulation of the coating cement and / or seal and / or the cement constituting the plugs before the steps coating and assembly of the structure as described in Example 2, or deposited by liquid or gaseous manner after said steps of coating / assembly of the structure as described in Example 3.
Le mode selon l'invention dans lequel l'hydrophobe ou l'oléophobe est incorporé à la formulation du ciment (et est donc au final présent dans la masse dudit ciment et/ou forme partie de celui-ci) présente l'avantage de ne pas nécessiter d'étape supplémentaire par rapport au procédé de fabrication du filtre incorporant un processus de dépôt de l'hydrophobe ou de l'oléophobe par voie gazeuse ou liquide. Notamment, l'étape de masquage permettant de déposer sélectivement celui-ci dans la porosité du ciment de revêtement et/ou de joint et/ou des bouchons n'est pas nécessaire.The mode according to the invention in which the hydrophobe or oleophobe is incorporated into the cement formulation (and is therefore ultimately present in the mass of said cement and / or forms part of it) has the advantage of not no need for additional step with respect to the method of manufacturing the filter incorporating a process of deposition of hydrophobic or oleophobic gas or liquid. In particular, the masking step for selectively depositing it in the porosity of the coating cement and / or seal and / or plugs is not necessary.
Le mode par incorporation ne peut le plus souvent être réalisé que dans des proportions limitées d'hydrophobe ou d'oléophobe, typiquement entre 0,1 et 10%, préférentiellement entre 0,5 et 6%, en masse par rapport à la masse sèche du ciment, selon la nature de l'ajout, la granulométrie de la poudre de graphite par exemple, ou le pouvoir hydrophobe, notamment l'angle de mouillage avec l'eau. En dessous de 0,1%, il a été observé que l'effet hydrophobe est insuffisant. Au delà de 10% l'ajout d'eau nécessaire à la mise en œuvre du ciment est trop élevée, ce qui conduit à des problèmes de fissuration lors du séchage du ciment et ensuite de la cohésion mécanique du filtre assemblé. Au delà de 10% peuvent aussi se poser des problèmes de dispersion de l'ajout incorporé remettant en cause l'homogénéité du ciment et de l'effet recherché. Des problèmes de prise ou de durcissement peuvent également se poser pour des ajouts trop élevés, voir des problèmes de moussage, qui ne sont pas solubles avec des agents anti-moussants.The embodiment by incorporation can most often be carried out only in limited proportions of hydrophobic or oleophobic, typically between 0.1 and 10%, preferably between 0.5 and 6% by weight relative to the dry mass cement, depending on the nature of the addition, the granulometry of the graphite powder, for example, or the hydrophobicity, especially the wetting angle with water. Below 0.1%, it has been observed that the hydrophobic effect is insufficient. Beyond 10% the addition of water required for the implementation of the cement is too high, which leads to problems of cracking during the drying of the cement and then the mechanical cohesion of the assembled filter. Beyond 10% may also arise problems of dispersion of the incorporated addition questioning the homogeneity of the cement and the desired effect. Caking or hardening problems can also arise for too high additions, see foaming problems, which are not soluble with anti-foaming agents.
Selon le mode dans lequel l'hydrophobe ou l'oléophobe est déposé par voie gazeuse, on peut, par exemple et comme décrit dans l'exemple 3, vaporiser celui-ci à basse température puis le redéposer à la surface du ciment, avantageusement uniquement sur des parties non masquées du filtre.According to the mode in which the hydrophobe or oleophobe is deposited by gaseous route, it is possible, for example and as described in Example 3, to vaporize it at low temperature and then redeposit it on the surface of the cement, advantageously only on unmasked parts of the filter.
Selon une variante du procédé d'obtention du filtre, celui-ci comprend des étapes : de fabrication d'une première structure telle que précédemment décrite, dans laquelle le ciment de revêtement, de préférence le ciment de joint et éventuellement le ciment constituant les bouchons comprennent un matériau oléophobe, d' imprégnation de ladite structure par une solution contenant un précurseur du catalyseur ou le catalyseur solubilisé dans un solvant hydrophobe tel qu'un hydrocarbure ou une huile, soit une suspension de particules catalytiques dans une solution contenant un solvant non polaire tels qu'une huile ou un hydrocarbure ou des tensioactifs .According to a variant of the process for obtaining the filter, it comprises steps of: manufacturing a first structure as previously described, in which the coating cement, preferably the joint cement and possibly the cement constituting the plugs; comprise an oleophobic material, impregnating said structure with a solution containing a precursor of the catalyst or the catalyst solubilized in a hydrophobic solvent such as a hydrocarbon or an oil, or a suspension of catalytic particles in a solution containing a non-polar solvent such as an oil or a hydrocarbon or surfactants.
De la même façon que précédemment, un tel procédé permet de minimiser la quantité de catalyseur utilisée lors de l'étape d'imprégnation de la structure.In the same way as above, such a method makes it possible to minimize the amount of catalyst used during the step of impregnating the structure.
Le matériau oléophobe est par exemple compris dans le groupe constitué par les silanes, les siloxanes, les siliconates, les composés organofluorés de faible tension superficielle. Le matériau oléophobe est par exemple un polymère fluoré ou un dérivé de silanes, ou un mélange de silane et fluorosilane comme le Z-6707 silane® de la société Dow Corning, ou encore un fluoropolymère tel que Zonyl MP 1400® de la société Du Pont Germany, sous la forme d'une poudre de diamètre médian des particules de 12 μm environ. De manière générale, les produits qui conviennent sont ceux ayant une tension superficielle critique inférieure à la tension superficielle de la solution dans laquelle le catalyseur est solubilisé. L'incorporation du matériau oléophobe peut se faire selon les mêmes principes et techniques que précédemment décrits pour l'incorporation du matériau hydrophobe .The oleophobic material is for example included in the group consisting of silanes, siloxanes, siliconates, organofluorinated compounds of low surface tension. The oleophobic material is, for example, a fluorinated polymer or a silane derivative, or a mixture of silane and fluorosilane such as Z-6707 silane® from Dow Corning, or a fluoropolymer such as Zonyl MP 1400® from Du Pont Germany, in the form of a powder with a median diameter of particles of about 12 microns. In general, the products which are suitable are those having a critical surface tension lower than the surface tension of the solution in which the catalyst is solubilized. The incorporation of the oleophobic material can be done according to the same principles and techniques as previously described for the incorporation of the hydrophobic material.
Selon l'invention, ladite imprégnation de la structure par le liquide polaire ou non polaire contenant le catalyseur ou un précurseur du catalyseur peut être effectuée par toute méthode connue de l'art et notamment par pompage de la solution au travers de la structure, par application d'un vide ou d'une dépression ou sous la pression du liquide comprenant la solution d' imprégnation sur au moins une extrémité de la structure. Une meilleure imprégnation est en général obtenue par une combinaison de ces différentes techniques, au cours d'étapes successives, le plus souvent une étape finale permettant l'élimination de la solution en excès dans le filtre par aspiration ou par introduction d'air sous pression.According to the invention, said impregnation of the structure with the polar or nonpolar liquid containing the catalyst or a precursor of the catalyst can be carried out by any method known in the art and in particular by pumping the solution through the structure, by applying a vacuum or a vacuum or under the pressure of the liquid comprising the impregnating solution on at least one end of the structure. Better impregnation is generally achieved by a combination of these different techniques, in successive steps, usually a final step allowing the removal of the excess solution in the filter by suction or by introduction of pressurized air .
Selon l'invention, l'étape d'imprégnation peut être mise en œuvre selon les procédés et/ou dispositifs connus de l'art antérieur et notamment selon un des procédés ou dispositifs décrits dans les brevets ou demandes de brevet précédemment cités .According to the invention, the impregnation step may be implemented according to the methods and / or devices known from the prior art and in particular according to one of the methods or devices described in the patents or patent applications mentioned above.
L'invention se rapporte selon un troisième aspect au filtre catalytique obtenu par le procédé de fabrication tel qu'il vient d'être décrit et qui se caractérise par la présence d'un matériau hydrophobe ou oléophobe à la surface et de préférence dans la porosité du ciment de revêtement et/ou de joint, ainsi que par la présence d'une quantité minime de catalyseur sur ledit ciment. Par quantité minime, il est entendu au sens de la présente description une quantité inférieure de catalyseur par rapport à la quantité de catalyseur présente au sein des parois filtrantes du filtre, c'est-à-dire au sein des éléments monolithiques en nid d'abeille.According to a third aspect, the invention relates to the catalytic filter obtained by the manufacturing method as just described and which is characterized by the presence of a hydrophobic or oleophobic material on the surface and preferably in porosity. coating and / or joint cement, as well as by the presence of a minimal amount of catalyst on said cement. In the sense of the present description, a minor amount is understood to mean a smaller amount of catalyst relative to the amount of catalyst present in the filtering walls of the catalyst. filter, that is to say within the monolithic elements in honeycomb.
L'invention et ses avantages seront mieux compris à la lecture des exemples qui suivent. Il est bien entendu que ces exemples ne doivent être considérés, sous aucun des aspects décrits, comme limitatifs de la présente invention.The invention and its advantages will be better understood on reading the examples which follow. It is understood that these examples should not be considered, in any of the aspects described, as limiting the present invention.
Exemple 1 :Example 1
Une structure filtrante comprenant un assemblage d'éléments filtrants en carbure de silicium liés par un ciment joint a été synthétisée selon les techniques décrites dans le brevetA filtering structure comprising an assembly of filter elements made of silicon carbide bonded with a joint cement was synthesized according to the techniques described in the patent
EP 1 142 619.EP 1 142 619.
Seize éléments filtrants monolithiques de section carrée sont d'abord extrudés, séchés puis cuits selon des techniques bien connues, par exemple décrites dans EP 1 142 619.Sixteen monolithic filter elements of square section are first extruded, dried and then cooked according to well-known techniques, for example described in EP 1 142 619.
Un ciment pour le joint et le revêtement est ensuite préparé en mélangeant :A cement for the joint and the coating is then prepared by mixing:
85% poids d'une poudre de SiC de granulométrie comprise entre 10 et 200 μm,85% by weight of a SiC powder having a particle size of between 10 and 200 μm,
4% poids d'une poudre d'alumine calcinée commercialisée par la société Almatis,4% by weight of a calcined alumina powder marketed by Almatis,
10% poids d'une poudre d'alumine réactive commercialisée par la société Almatis,10% by weight of a reactive alumina powder marketed by Almatis,
0,9% poids d'un liant temporaire et plastifiant du type Cellulose,0.9% by weight of a temporary binder and plasticizer of the Cellulose type,
0,1% poids d'un défloculant du type TPPNa0.1% weight of a deflocculant of the TPPNa type
(Tripolyphosphate de sodium) .(Sodium tripolyphosphate).
On additionne une quantité d'eau correspondant à 10% du poids de ce mélange pour obtenir un ciment de viscosité adéquate .A quantity of water corresponding to 10% of the weight of this mixture is added to obtain a cement of adequate viscosity.
Après assemblage des monolithes au moyen dudit ciment puis usinage de la surface extérieure de la structure ainsi obtenue, celle ci est ensuite recouverte du même ciment pour son revêtement. L'ensemble est recuit à une température suffisante pour assurer une cohésion satisfaisante du filtre et de ses éléments .After assembly of the monoliths by means of said cement and machining of the outer surface of the structure thus obtained, it is then covered with the same cement for its coating. The assembly is annealed at a temperature sufficient to ensure satisfactory cohesion of the filter and its elements.
Les caractéristiques de la structure de filtration brute ainsi synthétisée sont reportées dans le tableau 1.The characteristics of the crude filtration structure thus synthesized are reported in Table 1.
Tableau 1 : caractéristiques de la structure bruteTable 1: characteristics of the gross structure
(avant imprégnation)(before impregnation)
Cette structure brute est ensuite plongée dans un bain d'une solution aqueuse contenant les proportions appropriées d'un précurseur du Platine sous la forme H2PtCIo, et d'un précurseur de l'oxyde de cérium CeO2 (sous la forme nitrate de cérium) et d'un précurseur de l'oxyde de zirconium ZrO2 (sous la forme nitrate de zirconyl) selon les principes décrits dans la publication EP 1 338 322 Al. Le filtre est imprégné par la solution selon un mode de mise en œuvre similaire à celui décrit dans le brevet US 5,866,210. Le filtre est ensuite séché à environ 15O0C puis chauffé à une température d'environ 6000C. L'analyse chimique montre une concentration en Pt totale de 52 g/ft3 (1 g/ft3 = 0,035 kg/m3), soit 4,5 grammes répartis de façon non homogène sur les différentes parties du filtre.This crude structure is then immersed in a bath of an aqueous solution containing the appropriate proportions of a platinum precursor in the form of H 2 PtClO, and a precursor of cerium oxide CeO 2 (in the nitrate form of cerium) and a precursor of zirconium oxide ZrO 2 (in the form of zirconyl nitrate) according to the principles described in the publication EP 1 338 322 A1. The filter is impregnated with the solution according to an implementation mode. similar to that described in US Patent 5,866,210. The filter is then dried at about 150 ° C. and then heated to a temperature of about 600 ° C. The chemical analysis shows a total Pt concentration of 52 g / ft 3 (1 g / ft 3 = 0.035 kg / m 3 ), ie 4.5 grams unevenly distributed over the different parts of the filter.
Plus précisément, l'analyse révèle la répartition suivante :More specifically, the analysis reveals the following distribution:
0,25% poids de platine dans les éléments en nid d'abeille, soit 4,0 grammes,0.25% weight of platinum in the honeycomb elements, ie 4.0 grams,
0,13% poids de platine dans le ciment de revêtement, soit 0,25 grammes, sur une épaisseur de quelques dizaines de μm à partir de la surface extérieure du ciment,0.13% weight of platinum in the coating cement, ie 0.25 grams, over a thickness of a few tens of μm from the external surface of the cement,
0,08% poids de platine dans le ciment joint, soit 0,25 grammes, le platine étant réparti de façon homogène dans toute l'épaisseur du ciment.0.08% weight of platinum in the cement joint, ie 0.25 grams, the platinum being homogeneously distributed throughout the thickness of the cement.
Exemple 2 :Example 2
Un filtre catalytique a été fabriqué en répétant les mêmes étapes que ceux de l'exemple 1, à la différence que cette fois la formulation du ciment a été modifiée comme suit en incorporant une poudre de graphite hydrophobe :A catalytic filter was manufactured by repeating the same steps as those of Example 1, with the difference that this time the cement formulation was modified as follows by incorporating a hydrophobic graphite powder:
80% en poids d'une poudre de SiC de granulométrie comprise entre 10 et 200 μm,80% by weight of a SiC powder with a particle size of between 10 and 200 μm,
3,5% en poids d'une poudre d'alumine calcinée commercialisée par la société Almatis,3.5% by weight of a calcined alumina powder marketed by Almatis,
9% en poids d'une poudre d'alumine réactive commercialisée par la société Almatis,9% by weight of a reactive alumina powder marketed by Almatis,
5,4% graphite type Timrex@ KS75 de Timcal (poudre à5.4% graphite type Timrex @ KS75 from Timcal (powder
99,9% synthétique 2,24 de densité, de surface BET99.9% synthetic 2.24 density, BET surface
6, 5m2 /g, dont 90% massique des particules ont un diamètre inférieur à 60 microns,6, 5m 2 / g, 90% mass of the particles of which have a diameter of less than 60 microns,
2% en poids d'un liant temporaire et d'un plastifiant du type Cellulose, 0,1% poids d'un défloculant du type TPPNa (Tripolyphosphate de sodium) .2% by weight of a temporary binder and a plasticizer of the Cellulose type, 0.1% by weight of a deflocculant of the TPPNa type (sodium tripolyphosphate).
On additionne une quantité d'eau correspondant environ à 15% du poids de ce mélange pour obtenir un ciment de viscosité adéquate. Après assemblage des monolithes au moyen dudit ciment puis usinage de la surface extérieure de la structure ainsi obtenue, celle ci est ensuite recouverte du même ciment pour son revêtement. L'ensemble est recuit à une température suffisante pour assurer une cohésion satisfaisante du filtre.A quantity of water corresponding to approximately 15% of the weight of this mixture is added to obtain a cement of adequate viscosity. After assembly of the monoliths by means of said cement and machining of the outer surface of the structure thus obtained, it is then covered with the same cement for its coating. The assembly is annealed at a temperature sufficient to ensure satisfactory cohesion of the filter.
Les caractéristiques de la structure brute et du filtre obtenu après imprégnation selon cet exemple sont sensiblement les mêmes que ceux obtenus pour l'exemple 1 et répertoriés dans le tableau 1.The characteristics of the crude structure and the filter obtained after impregnation according to this example are substantially the same as those obtained for Example 1 and listed in Table 1.
L'analyse chimique montre une concentration en Pt totale de 49 g/ft3, soit 4,3 grammes répartis sur les différentes parties du filtre.The chemical analysis shows a total concentration of Pt 49 g / ft 3 , or 4.3 grams distributed over the different parts of the filter.
Plus précisément, l'analyse révèle la répartition suivante :More specifically, the analysis reveals the following distribution:
0,25% poids de platine dans les éléments en nid d'abeille, soit 4,0 grammes,0.25% weight of platinum in the honeycomb elements, ie 4.0 grams,
0,07% poids de platine dans le ciment de revêtement soit 0,15 grammes,0.07% weight of platinum in the coating cement, ie 0.15 grams,
0,10% poids de platine dans le ciment joint, soit 0,15 grammes.0.10% weight of platinum in the cement joint, ie 0.15 grams.
On montre ainsi qu'en incorporant dans le ciment une faible quantité d'un matériau hydrophobe avant l'étape d'imprégnation dans la solution aqueuse du catalyseur, il est possible de réaliser au final une économie substantielle de Pt. Plus exactement, la comparaison des résultats obtenus selon les exemples 1 et 2 montre que l'application du procédé selon l'invention permet d'économiser une quantité non négligeable de catalyseur et en particulier de métal précieuxIt is thus shown that by incorporating into the cement a small amount of a hydrophobic material before the impregnation step in the aqueous solution of the catalyst, it is possible to finally achieve a substantial saving in Pt. More exactly, the comparison results obtained according to Examples 1 and 2 shows that the application of the method according to the invention makes it possible to save a quantity negligible catalyst and especially precious metal
(0,2 grammes par filtre), générant ainsi une économie substantielle du coût global du procédé de dépôt de catalyseur sur la structure.(0.2 grams per filter), thereby generating a substantial saving in the overall cost of the catalyst deposition process on the structure.
Exemple 3 :Example 3
Un filtre catalytique a été fabriqué en répétant les mêmes étapes que ceux de l'exemple 1. Des masques sont ensuite appliqués sur les parties du filtre sur lesquels on ne souhaite pas déposer l'agent hydrophobe, c'est-à-dire les parties autres que les joints apparents de ciment entre éléments et le ciment de revêtement du filtre. Les masques ont été soigneusement découpés et placés manuellement, en raisons des irrégularités des surfaces avant et arrière du filtre, inhérente au procédé d'assemblage des éléments. Le filtre ainsi masqué est ensuite placé dans un dessiccateur sur une plaque support. Est déposé au fond du dessiccateur environ 0,5 ml de perfluorodecyltrichlorosilane par filtre. Le réacteur est ensuite fermé et chauffé jusqu'à une température de 1000C avec une pression résiduelle de 0,1 mbar environ (1 bar = 0,1 MPa) . Cette procédure permet de vaporiser le silane qui se dépose ensuite sur les parties non masquées. Après enlèvement des masques, cette structure brute est ensuite plongée dans un bain d'une solution aqueuse comme dans l'exemple 1.A catalytic filter was manufactured by repeating the same steps as those of Example 1. Masks are then applied to the parts of the filter on which it is not desired to deposit the hydrophobic agent, that is to say the parts other than the apparent cement joints between elements and the filter coating cement. The masks were carefully cut and placed manually, because of the irregularities of the front and back surfaces of the filter, inherent to the assembly process of the elements. The masked filter is then placed in a desiccator on a support plate. About 0.5 ml of perfluorodecyltrichlorosilane is deposited on the bottom of the desiccator by filter. The reactor is then closed and heated to a temperature of 100 ° C. with a residual pressure of approximately 0.1 mbar (1 bar = 0.1 MPa). This procedure is used to vaporize the silane which is then deposited on the unmasked parts. After removal of the masks, this raw structure is then immersed in a bath of an aqueous solution as in Example 1.
L'analyse chimique montre une concentration en Pt totale de 48 g/ft3, soit 4,2 grammes répartis sur les différentes parties du filtre.The chemical analysis shows a total concentration of Pt of 48 g / ft 3 , ie 4.2 grams distributed over the different parts of the filter.
Plus précisément, l'analyse révèle la répartition suivante :More specifically, the analysis reveals the following distribution:
0,25% poids de platine dans les éléments en nid d'abeille, soit 4,0 grammes, 0,07% poids de platine dans le ciment de revêtement soit 0,1 grammes,0.25% weight of platinum in the honeycomb elements, ie 4.0 grams, 0.07% weight of platinum in the coating cement, ie 0.1 grams,
0,04% poids de platine dans le ciment joint, soit 0,1 grammes.0.04% weight of platinum in the cement joint, ie 0.1 grams.
La comparaison des résultats obtenus selon les exemples 1 et 3 montre que l'application du procédé selon l'invention peut permettre d'économiser une quantité non négligeable de catalyseur et en particulier de métal précieux (0,3 grammes par filtre) , générant ainsi une économie substantielle du coût global du procédé de dépôt de catalyseur sur la structure .The comparison of the results obtained according to Examples 1 and 3 shows that the application of the process according to the invention can make it possible to save a not insignificant amount of catalyst and in particular of precious metal (0.3 grams per filter), thereby generating a substantial saving in the overall cost of the catalyst deposition process on the structure.
Il est bien entendu que la présente invention ne se résume pas à ce simple mode de réalisation et que tout moyen connu d'agir sur le caractère hydrophobe ou oléophobe des ciments de joint/revêtement doit être considéré comme compris dans le cadre de la présente invention. It is understood that the present invention is not limited to this simple embodiment and that any known means to act on the hydrophobic or oleophobic character of the joint cements / coating should be considered as part of the present invention .

Claims

REVENDICATIONS
1. Structure utilisable, après dépôt d'un catalyseur, pour la filtration d'un gaz chargé en particules de suies et de polluants en phase gazeuse et comprenant :1. A structure that can be used, after deposition of a catalyst, for the filtration of a gas charged with particles of soot and pollutants in the gas phase and comprising:
- une partie centrale comprenant une pluralité d'éléments filtrants en nid d'abeille reliés entre eux par un ciment de joint, le ou lesdits éléments comprenant un ensemble de conduits ou canaux adjacents d'axes parallèles entre eux séparés par des parois poreuses, lesquels conduits étant obturés par des bouchons à l'une ou l'autre de leurs extrémités pour délimiter des chambres d'entrée s ' ouvrant suivant une face d'admission des gaz et des chambres de sortie s ' ouvrant suivant une face d'évacuation des gaz, de telle façon que le gaz traverse les parois poreuses eta central part comprising a plurality of honeycomb filter elements interconnected by a joint cement, the one or more elements comprising a set of adjacent ducts or channels with axes parallel to one another separated by porous walls, which conduits being closed by plugs at one or the other of their ends to define inlet chambers opening on a gas inlet face and outlet chambers opening on a discharge face of gas, so that the gas passes through the porous walls and
- une partie périphérique constituée par un ciment de revêtement protégeant lesdits éléments, ladite structure se caractérisant en ce que le ciment de revêtement, de préférence le ciment de joint et éventuellement le ciment constituant les bouchons comprennent au moins en surface et de préférence dans la porosité un matériau hydrophobe ou oléophobe.- A peripheral portion constituted by a coating cement protecting said elements, said structure being characterized in that the coating cement, preferably the joint cement and optionally the cement constituting the plugs comprise at least on the surface and preferably in the porosity a hydrophobic or oleophobic material.
2. Structure selon la revendication 1, constituée par un bloc filtrant associant plusieurs éléments filtrants monolithiques en nid d'abeille, lesdits éléments étant assemblés et collés par un ciment de joint comprenant un matériau hydrophobe ou oléophobe.2. Structure according to claim 1, consisting of a filter block associating several monolithic honeycomb filter elements, said elements being assembled and bonded by a joint cement comprising a hydrophobic or oleophobic material.
3. Structure selon la revendication 1 ou 2, dans laquelle lesdits éléments, le ciment de revêtement et de préférence le ciment de joint et/ou le ciment constituant les bouchons sont à base d'un même matériau céramique, préférentiellement à base de carbure de silicium SiC.3. Structure according to claim 1 or 2, wherein said elements, the coating cement and preferably the joint cement and / or the cement constituting the plugs are based on the same ceramic material, preferably based on silicon carbide SiC.
4. Procédé d'obtention d'un filtre pour la filtration d'un gaz chargé en particules de suies et de polluants en phase gazeuse tel que l'oxyde de carbone CO, les oxydes d'azote NOx, les oxydes de soufre SOx, les hydrocarbures HC, ledit procédé comprenant les étapes :4. Process for obtaining a filter for the filtration of a gas charged with soot particles and gas phase pollutants such as CO carbon monoxide, NOx nitrogen oxides, SOx sulfur oxides, HC hydrocarbons, said process comprising the steps of:
- de fabrication d'une première structure selon l'une des revendications 1 à 3, dans laquelle le ciment de revêtement et de préférence le ciment de joint et éventuellement le ciment constituant les bouchons comprennent un matériau hydrophobe, d' imprégnation de ladite structure par une solution contenant un précurseur du catalyseur ou le catalyseur solubilisé dans un solvant polaire tel que l'eau, soit une suspension de particules catalytiques dans un solvant polaire tel que l'eau.- Manufacturing a first structure according to one of claims 1 to 3, wherein the coating cement and preferably the joint cement and optionally the cement constituting the plugs comprise a hydrophobic material, impregnation of said structure by a solution containing a precursor of the catalyst or the catalyst solubilized in a polar solvent such as water, a suspension of catalytic particles in a polar solvent such as water.
5. Procédé selon la revendication 4, dans lequel le matériau hydrophobe se présente sous forme d'une poudre d'un matériau compris dans le groupe constitué par le carbone graphite, CaF2, ou d'autres poudres minérales hydrophobes contenant l'élément fluor.5. The method of claim 4, wherein the hydrophobic material is in the form of a powder of a material comprised in the group consisting of graphite carbon, CaF 2 , or other hydrophobic mineral powders containing the fluorine element. .
6. Procédé selon la revendication 4, dans lequel le matériau hydrophobe comprend au moins un composé organique ou organométallique choisi parmi les sels métalliques d'acides gras C12-C20 comme les stéarates ou les oléates d'alcalins ou d' alcalino-terreux, les silicones, les silanes, les siloxanes, les siliconates, les composés organofluorés de faible tension superficielle dont les poudres de PTFE, les résines acryliques et vinyliques, les huiles paraffiniques . 6. Process according to claim 4, in which the hydrophobic material comprises at least one organic or organometallic compound chosen from metal salts of C12-C20 fatty acids such as alkali or alkaline earth stearates or oleates, silicones, silanes, siloxanes, siliconates, organofluorinated compounds of low surface tension including PTFE powders, acrylic and vinyl resins, paraffinic oils.
7. Procédé d'obtention d'un filtre pour la filtration d'un gaz chargé en particules de suies et de polluants en phase gazeuse tel que l'oxyde de carbone CO, les oxydes d'azote NOx, les oxydes de soufre SOx, les hydrocarbures HC, ledit procédé comprenant les étapes :7. Process for obtaining a filter for the filtration of a gas loaded with soot particles and gas phase pollutants such as CO carbon monoxide, NOx nitrogen oxides, SOx sulfur oxides, HC hydrocarbons, said process comprising the steps of:
- de fabrication d'une première structure selon l'une des revendications 1 à 3, dans laquelle le ciment de revêtement et de préférence le ciment de joint et éventuellement le ciment constituant les bouchons comprennent un matériau oléophobe, d' imprégnation de ladite structure par une solution contenant un précurseur du catalyseur ou le catalyseur solubilisé dans un solvant hydrophobe tel qu'un hydrocarbure ou une huile, soit une suspension de particules catalytiques dans un solvant tel qu'un hydrocarbure ou une huile.- Manufacturing a first structure according to one of claims 1 to 3, wherein the coating cement and preferably the joint cement and optionally the cement constituting the caps comprise an oleophobic material impregnation of said structure by a solution containing a precursor of the catalyst or the catalyst solubilized in a hydrophobic solvent such as a hydrocarbon or an oil, or a suspension of catalytic particles in a solvent such as a hydrocarbon or an oil.
8. Procédé selon la revendication 7, dans lequel le matériau oléophobe est compris dans le groupe constitué par les silanes, les siloxanes, les siliconates, les composés organofluorés de faible tension superficielle.8. The method of claim 7, wherein the oleophobic material is included in the group consisting of silanes, siloxanes, siliconates, organofluorinated compounds of low surface tension.
9. Procédé selon l'une des revendications 4 à 8 dans lequel l' hydrophobe ou l' oléophobe est incorporé dans la formulation du ciment de revêtement et/ou de joint avant l'étape de revêtement et d'assemblage de la structure.9. Method according to one of claims 4 to 8 wherein the hydrophobe or oleophobe is incorporated in the formulation of the coating cement and / or seal before the step of coating and assembly of the structure.
10. Procédé selon l'une des revendications 4 à 8 dans lequel l' hydrophobe ou l' oléophobe est incorporé après l'étape de revêtement et d'assemblage de la structure par voie liquide ou gazeuse par dépôt sur la structure sous forme liquide ou sous forme gazeuse. 10. Method according to one of claims 4 to 8 wherein the hydrophobe or oleophobe is incorporated after the step of coating and assembling the structure by liquid or gaseous process by depositing on the structure in liquid form or in gaseous form.
11. Procédé selon l'une des revendication 4 à 10, dans lequel ladite imprégnation peut être effectuée par pompage de la solution au travers de la structure, par application d'un vide ou d'une dépression ou sous la pression du liquide comprenant la solution d' imprégnation sur au moins une extrémité de la structure ou par une combinaison de ces différentes techniques.11. The method according to one of claims 4 to 10, wherein said impregnation can be performed by pumping the solution through the structure, by applying a vacuum or a vacuum or under the pressure of the liquid comprising the impregnation solution on at least one end of the structure or a combination of these different techniques.
12. Filtre catalytique susceptible d'être obtenu par le procédé selon l'une des revendications 7 à 11 se caractérisant par la présence d'un matériau hydrophobe ou oléophobe à la surface et de préférence dans la porosité dudit le ciment de revêtement et/ou de joint, ainsi que par la présence d'une quantité minime de catalyseur au niveau dudit ciment. 12. Catalytic filter obtainable by the method according to one of claims 7 to 11 characterized by the presence of a hydrophobic or oleophobic material on the surface and preferably in the porosity of said coating cement and / or seal, as well as the presence of a minimal amount of catalyst at said cement.
EP06778932A 2005-06-14 2006-06-13 Structure and catalytic filter for filtering a gas comprising a hydrophobic or oleophobic cement Withdrawn EP1890811A2 (en)

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FR0551595A FR2886869B1 (en) 2005-06-14 2005-06-14 STRUCTURE AND CATALYTIC FILTER FOR FILTERING GAS COMPRISING HYDROPHOBIC OR OLEOPHOBIC CEMENT
PCT/FR2006/050554 WO2006134303A2 (en) 2005-06-14 2006-06-13 Structure and catalytic filter for filtering a gas comprising a hydrophobic or oleophobic cement

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EP (1) EP1890811A2 (en)
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WO2006134303A2 (en) 2006-12-21
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WO2006134303A3 (en) 2007-02-22
US20090297407A1 (en) 2009-12-03
JP2008546517A (en) 2008-12-25

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