Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
  • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
  • B01D53/9404—Removing only nitrogen compounds
  • B01D53/9409—Nitrogen oxides
  • B01D53/9413—Processes characterised by a specific catalyst
  • B01D53/9422—Processes characterised by a specific catalyst for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)
• • 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
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
  • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
  • B01J23/56—Platinum group metals
  • B01J23/63—Platinum group metals with rare earths or actinides
• • 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
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/32—Manganese, technetium or rhenium
  • B01J23/34—Manganese
• • 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
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
  • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
  • B01J23/56—Platinum group metals
  • B01J23/64—Platinum group metals with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/202—Alkali metals
  • B01D2255/2022—Potassium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/204—Alkaline earth metals
  • B01D2255/2042—Barium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/207—Transition metals
  • B01D2255/2073—Manganese

Definitions

• the present invention relates to a composition which can be used as a NOx trap, based on manganese and an alkaline earth or a rare earth and its use in the treatment of exhaust gases.
• NOx traps potassium based in particular, which are capable of oxidizing NO to O2 and then adsorbing the NO2 thus formed. Under certain conditions, NO2 is released and then reduced to N2 by reducing species contained in the exhaust gases. These NOx traps still have certain drawbacks, however. Thus, they age badly in the sense that their operation is less satisfactory when they are subjected to high temperatures. Furthermore, they may have a low resistance to sulfation.
• the object of the invention is therefore to provide NOx traps which have improved resistance to aging.
• the composition which can be used as a NOx trap comprises a support and an active phase, and it is characterized in that the active phase is based on manganese and at least one other element A chosen among alkaline earths and rare earths, and in that it presents or is likely to have a specific surface of at least 10m 2 / g after calcination for 8 hours at 800 ° C.
• the composition of the invention comprises a support and an active phase.
• support must be taken in a broad sense to designate, in the composition, the majority element (s) and / or either without catalytic activity or own trapping activity, or having a catalytic activity or trapping not equivalent to that of the phase active; and on which or on which the other elements are deposited.
• support and active or supported phase we will speak in the following description of support and active or supported phase but it will be understood that it would not go beyond the scope of the present invention in the case where an element described as belonging to the active or supported phase was present in the support, for example by having been introduced into it during the preparation of the support itself.
• the active phase of the composition is based on manganese and at least one element A.
• This element A can be an alkaline earth or a rare earth.
• alkaline earth there may be mentioned more particularly barium.
• the rare earth can be more particularly chosen from cerium, terbium, gadolinium, samarium, neodymium and praseodymium.
• the total manganese, alkaline earth or rare earth contents can vary between 1 and 50%, more particularly between 5 and 30%. These proportions are expressed in atomic% relative to the sum of the moles of oxide (s) of the support and of the elements concerned of the supported phase.
• the respective manganese, alkaline-earth or rare earth contents can also vary within wide proportions, the manganese content can in particular be equal or close to that of element A.
• the invention covers the case where the active phase consists essentially of manganese and one or more other elements A chosen from alkaline earths and rare earths.
• consists essentially is meant that the composition of the invention can have a NOx trap activity in the absence in the active phase of any element other than manganese and the element (s) A, such as for example an element of type precious metal or other metal usually used in catalysis.
• a characteristic of the composition is that it has or is likely to have a specific surface of at least 10 m / g after calcination for 8 hours at 800 ° C.
• This specific surface may in particular be at least 20 m 2 / g after calcination at the same temperature and for the same duration. More
• this specific surface is at least 80 m / g and even more
• the term “specific surface” is understood to mean the BET specific surface area determined by nitrogen adsorption in accordance with standard ASTM D 3663-78 established on the basis of the BRUNAUER - EMMETT-TELLER method described in the periodical "The Journal of the American Chemical Society, 60 , 309 (1938) ". This surface characteristic is obtained by the choice of a suitable support, in particular having a sufficiently high specific surface.
• This support can be based on alumina. Any type of alumina capable of having a specific surface sufficient for application in catalysis can be used here. Mention may be made of aluminas resulting from the rapid dehydration of at least one aluminum hydroxide, such as bayerite, hydrargillite or gibbsite, nordstrandite, and / or from at least one aluminum oxyhydroxide such as boehmite , pseudoboehmite and diaspore.
• aluminum hydroxide such as bayerite, hydrargillite or gibbsite, nordstrandite
• at least one aluminum oxyhydroxide such as boehmite , pseudoboehmite and diaspore.
• a stabilized alumina is used.
• stabilizing element mention may be made of rare earths, barium, silicon and zirconium.
• rare earth there may be mentioned very particularly cerium, lanthanum or the lanthanum-neodymium mixture.
• the preparation of the stabilized alumina is carried out in a manner known per se, in particular by impregnating the alumina with solutions of salts, such as nitrates, of the abovementioned stabilizing elements or else by co-drying of an alumina precursor and salts of these elements then calcination.
• salts such as nitrates
• Curing can be done by alumina in water suspension and then heating at a temperature of for example between 70 C and 110 C. After curing, the alumina is subjected to a heat treatment.
• Another preparation consists of a similar type of treatment but with barium.
• the stabilizer content expressed by weight of stabilizer oxide relative to the stabilized alumina is generally between 1.5 and 15%, more particularly between 2.5 and 11%.
• the support can also be based on silica. It can also be based on silica and titanium oxide in an atomic proportion Ti / Ti + Si of between 0.1 and 15%. This proportion can be more particularly between 0.1 and 10%.
• a support is described in particular in patent application WO 99/01216, the teaching of which is incorporated here.
• cerium oxide and zirconium oxide can be used, these oxides possibly being in the form of a mixed oxide or of a solid solution of zirconium oxide in l cerium oxide or vice versa.
• These supports are obtained by a first type of process which comprises a step in which a mixture comprising zirconium oxide and cerium oxide is formed and the mixture thus formed is washed or impregnated with an alkoxylated compound having a number of carbon atoms greater than 2. The impregnated mixture is then calcined.
• the alkoxylated compound can be chosen in particular from the products of formula (2) R ⁇ - ((CH2) ⁇ -O) n-R2 in which Ri and R2 represent alkyl groups, linear or not, or H or OH or Cl or Br or I; n is a number between 1 and 100; and x is a number between 1 and 4, or else those of formula (3) (R3, R4) - ⁇ - ((CH2) ⁇ -O) n - OH in which ⁇ denotes a benzene ring, R3 and R4 are identical or different substituents of this ring and represent hydrogen or linear or non-alkyl groups having from 1 to 20 carbon atoms, x and n being defined as above; or also those of formula (4) R4 ⁇ - ((CH2) ⁇ -O) n -H where R4 represents a linear or non-linear alcohol group having from 1 to 20 carbon atoms; x and n being defined as above; and those of formula (5) R5-S -
• These supports can also be obtained by a second type of process which comprises a step in which a solution of a cerium salt, a solution of a zirconium salt and an additive chosen from anionic surfactants, non-surfactants, are reacted. ionic, polyethylene glycols, carboxylic acids and their salts, the reaction possibly being able to take place in the presence of a base and / or an oxidizing agent.
• anionic surfactants carboxylates, phosphates, sulfates and sulfonates can be used more particularly.
• nonionic surfactants it is possible to use ethoxylated alkyl phenols and ethoxylated amines.
• the reaction between the zirconium and cerium salts can be done by heating the solution containing the salts, it is then a thermohydrolysis reaction. It can also be done by precipitation by introducing a base into the solution containing the salts.
• composition of the invention can be prepared by a process in which the support is brought into contact with manganese and at least one other element A or with precursors of manganese and at least one other element A and in which the together at a temperature sufficient to transform the precursors or the elements into oxides. Generally, this temperature is at least 500 ° C., more particularly at least 600 ° C.
• One method which can be used for the aforementioned contacting is impregnation. This first forms a solution or slip of salts or compounds of the elements of the supported phase.
• salts one can choose the salts of inorganic acids such as nitrates, sulfates or chlorides.
• salts of organic acids and in particular the salts of saturated aliphatic carboxylic acids or the salts of hydroxycarboxylic acids.
• the support is then impregnated with the solution or the slip.
• Dry impregnation consists in adding to the product to be impregnated a volume of an aqueous solution of the element which is equal to the pore volume of the solid to be impregnated.
• the support is optionally dried and then it is calcined. It should be noted that it is possible to use a support which has not yet been calcined prior to impregnation.
• the deposition of the active phase can also be done by atomization of a suspension based on salts or compounds of the elements of the active phase and of the support. The atomized product thus obtained is then calcined.
• composition of the invention as described above is in the form of a powder but it can optionally be shaped to be in the form of granules, beads, cylinders or honeycombs of variable dimensions.
• the invention also relates to a gas treatment process with a view to reducing the emissions of nitrogen oxides using the composition of the invention.
• gases capable of being treated in the context of the present invention are, for example, those from gas turbines, boilers of thermal power plants or even internal combustion engines. In the latter case, it may in particular be diesel engines or engines operating in a lean mixture.
• the composition of the invention functions as NOx traps when it is brought into contact with gases which have a high oxygen content.
• the value ⁇ is correlated with the air / fuel ratio in a manner known per se, in particular in the field of internal combustion engines.
• gases may be those of an engine operating in a lean burn mixture and which have an oxygen content (expressed by volume) for example of at least 2%, as well as those which have an even higher oxygen content, for example.
• oxygen content expressed by volume
• example of diesel engine gases that is to say at least 5% or more than 5%, more particularly at least 10%, this content being, for example, between 5% and 20%.
• the invention also applies to gases of the above type which may further contain water in an amount of the order of 10% for example.
• composition of the invention may be useful in the treatment of exhaust gases from internal combustion engines operating with a fuel containing sulfur, that is to say for fuels whose sulfur content is at least 50 ppm, more particularly at least 200 ppm (content expressed in sulfur element).
• sulfur must be taken in the broad sense, that is to say as designating sulfur but also the sulfur compounds which are present in fuels.
• the invention also relates to a catalytic system for the treatment of an exhaust gas from an internal combustion engine comprising a composition according to the invention. More specifically, this system comprises a coating (wash coat) with catalytic properties and incorporating said composition, this coating being deposited on a substrate of the type, for example metallic or ceramic monolith.
• the invention also relates to the use of a composition as described above in the manufacture of such a catalytic system. Examples will now be given.
• compositions were prepared as follows.
• Manganese nitrate Mn (N ⁇ 3) 2.4H 2 O, potassium nitrate KNO3 99.5%, barium nitrate Ba (NO3) 2 99.5% are used.
• the support used is an SB3 Condea alumina.
• Step i Deposit of the first active element: This step consists in depositing the active element Mn in an amount equal to 10 atomic% and calculated as follows:
• the elements are impregnated on the support one after the other according to the following operating protocol: - Dry impregnation of the first element
• This example shows the resistance to aging of a composition according to the invention.
• the catalytic test is carried out as follows:
• the WH is of the order of 150,000 h "
• the NO and NOx signals are given by an ECOPHYSICS NOx analyzer, based on the principle of chemiluminescence.
• the evaluation of NOx traps is carried out by determining the total amount (NSC) of adsorbed NOx (expressed in mg NO / g of trap or active phase) until the trap phase is saturated. The measurement is made at 250 ° C.
• compositions have undergone hydrothermal aging of the redox type according to the protocol which follows.
• compositions are raised in temperature under N 2 in 60 minutes to 950 ° C.
• the compositions are then maintained at this temperature for 6 hours, alternating 24 periods of 15 min in atmospheres of oxygen and water in nitrogen and of hydrogen and water in nitrogen respectively.
• the temperature drops under H 2 / N 2 to 80 ° C. and then under N 2 .
• composition according to the invention has improved resistance to aging.
• This example shows the sulfation resistance of a composition according to the invention.
• the same compositions (not aged) are used as those of Example 1.
• the reaction mixture at the inlet of the reactor has either the same composition as in Example 1 or this composition with in addition 30 ppm of SO 2 .
• composition according to the invention has improved resistance to SO 2 .

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Environmental & Geological Engineering (AREA)
• Health & Medical Sciences (AREA)
• Biomedical Technology (AREA)
• Combustion & Propulsion (AREA)
• Analytical Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Catalysts (AREA)
• Exhaust Gas Treatment By Means Of Catalyst (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)
• Exhaust Gas After Treatment (AREA)
• Treating Waste Gases (AREA)

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• 1999
  • 1999-04-23 FR FR9905187A patent/FR2792547B1/fr not_active Expired - Fee Related
• 2000
  • 2000-04-18 WO PCT/FR2000/001008 patent/WO2000064580A1/fr active Search and Examination
  • 2000-04-18 CN CN008079072A patent/CN1132681C/zh not_active Expired - Fee Related
  • 2000-04-18 JP JP2000613564A patent/JP2002542029A/ja active Pending
  • 2000-04-18 CA CA002371276A patent/CA2371276A1/fr not_active Abandoned
  • 2000-04-18 BR BR0009995-3A patent/BR0009995A/pt not_active IP Right Cessation
  • 2000-04-18 EP EP00920832A patent/EP1181094A1/de not_active Withdrawn
  • 2000-04-18 KR KR10-2001-7013538A patent/KR100420909B1/ko not_active IP Right Cessation
• 2001
  • 2001-10-22 NO NO20015161A patent/NO20015161L/no not_active Application Discontinuation
  • 2001-10-23 ZA ZA200108713A patent/ZA200108713B/en unknown

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