Classifications

• • 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
  • B01J37/024—Multiple impregnation or coating
  • B01J37/0248—Coatings comprising impregnated particles
• • 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
  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
  • B01J21/04—Alumina
• • 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
  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
  • B01J21/063—Titanium; Oxides or hydroxides thereof
• • 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
  • B01J23/48—Silver or gold
  • B01J23/50—Silver
• • 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
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
  • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
  • F01N3/206—Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents
• • 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
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
  • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
  • F01N3/2066—Selective catalytic reduction [SCR]
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2251/00—Reactants
  • B01D2251/20—Reductants
  • B01D2251/208—Hydrocarbons
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2251/00—Reactants
  • B01D2251/20—Reductants
  • B01D2251/21—Organic compounds not provided for in groups B01D2251/206 or B01D2251/208
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/10—Noble metals or compounds thereof
  • B01D2255/104—Silver
• • 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
  • B01D2255/20707—Titanium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/209—Other metals
  • B01D2255/2092—Aluminium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/30—Sulfur compounds
  • B01D2257/302—Sulfur oxides
• • 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
• • 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
  • F01N2610/00—Adding substances to exhaust gases
  • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
• • 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
  • F01N2610/00—Adding substances to exhaust gases
  • F01N2610/03—Adding substances to exhaust gases the substance being hydrocarbons, e.g. engine fuel
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
  • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/10—Internal combustion engine [ICE] based vehicles
  • Y02T10/12—Improving ICE efficiencies

Definitions

• the present invention relates to a catalyst or device for the reduction of nitrogen oxides in the presence of a reducing agent chosen from hydrocarbons, oxygenated compounds and their mixtures, in a gaseous effluent comprising sulfur oxides, and a process of preparing this catalyst and a method of reducing the corresponding nitrogen oxides.
• a reducing agent chosen from hydrocarbons, oxygenated compounds and their mixtures
• the combustion of fossil fuel such as oil or coal in a combustion system, particularly in an engine, can result in the production of significant quantities of pollutants that can be discharged into the environment and cause damage to the environment.
• pollutants nitrogen oxides, called NOx and mainly comprising NO and NO 2 , can be cited, as they are suspected to be one of the factors contributing to the formation of acid rain and deforestation.
• the main known method for removing NOx is to selectively reduce these compounds by means of so-called selective catalytic reduction (SCR) catalysts in the presence of a reducing agent.
• SCR selective catalytic reduction
• This reducing agent may be according to a first variant the ammonia which is generated for example from urea, or according to a second variant of the hydrocarbons or oxygenated compounds.
• the first variant presents the risk of inducing leakage of ammonia, and thus aggravate the pollution phenomena instead of limiting them.
• the supply of ammonia in mobile applications remains problematic.
• the most studied catalytic systems for the selective catalytic reduction of NOx are zeolite catalysts and silver-on-alumina catalysts.
• the catalyst used comprises a ferrierite exchanged with a rare earth chosen from cerium, praseodymium, samarium, terbium, europium and ytterbium.
• the application FR 09/56491 also describes a process for reducing NOx in a gaseous effluent using a catalyst based on alumina and titanium oxide comprising silver, the reducing agent used in this process being hydrocarbons and or oxygenated compounds.
• diesel used in diesel engines may contain significant amounts of sulfur derivatives, for example 1% by weight and more sulfur for gas oils used for boats, which is then in the exhaust gas under form of S0 2 at 400-500 ppm.
• the inventors have surprisingly discovered that it is possible to maintain the activity of a catalyst based on a mixture of alumina, titanium oxide and silver over time by increasing the silver content. of this catalyst, this content being between 3 and 10%, especially between 3 and 5%, such that> 3 and ⁇ 5% by weight of the total weight of the catalyst, and preferably between 3.5 and 4.5%.
• the invention therefore has for its first object a catalyst comprising a mixture of alumina, titanium oxide and silver, the silver content being between 3 and 10%, especially between 3 and 5%, such that greater than 3% and less than 5%, in particular between 3.5 and 4.5%, especially about 4%, by weight relative to the total weight of the support.
• the silver in the catalyst is in particular in the form of Ag + and Ag n 5+ clusters.
• Silver is the main active phase of this catalyst responsible for the reduction of NOx in the gaseous effluent.
• the catalyst comprises predominantly alumina (Al 2 O 3 - aluminum oxide).
• the mass ratio of the amount of alumina to the amount of titanium oxide is between 50:50 and 99.99: 0.01, especially between 90:10 and 99.99: 0.01, advantageously between 95: 5 and 99.95: 0.05, preferably between 98: 2 and 99.9: 0.1.
• This alumina also contributes to the reduction of NOx in the gaseous effluent.
• the catalyst according to the invention may comprise in particular less than 1 wt.%, Advantageously less than 0.5 wt.%, Preferably less than 0.1 wt.%, And ideally will be essentially free of materials other than alumina, titanium oxide and silver.
• the catalyst consists or consists essentially of a mixture of alumina, titanium oxide and silver with impurities, the amounts of silver being as defined above.
• the catalyst will in particular be obtainable by a preparation process as described below.
• the catalyst will advantageously be prepared in powder form.
• the catalyst can then be put in the form of pellets, extrusions, or beads or be deposited on a monolith.
• the catalyst will be mixed with a conventional binder such as clay, alumina or silica gel.
• the present invention therefore also relates to a device comprising a catalyst according to the invention in the form of extrudates, pellets or balls.
• the present invention therefore also relates to a device comprising a catalyst as described above deposited on a monolith, in particular porous, in particular in the form of a honeycomb.
• the monolith may be a monolith of ceramics, the ceramics may be cordierite, or a metallic monolith.
• the monolith may include channels to allow the passage of the gaseous effluent to be treated through the monolith, the channels passing through the monolith from one side to the other.
• the above catalyst and therefore also the above device, is particularly suitable for use in the context of a selective catalytic reduction reaction of nitrogen oxides with hydrocarbons and / or oxygenated compounds, especially in a gaseous effluent comprising sulfur oxides, and advantageously S0 2 .
• the NOx selective reduction reaction can be carried out by simply bringing into contact a gaseous effluent containing NOx, as well as hydrocarbons and / or oxygenated compounds, with the above catalyst and at a reaction temperature that is more particularly understood. between 200 and 500 ° C, and preferably between 300 and 450 ° C.
• the catalyst above is particularly applicable in the context of the treatment of the exhaust gas of an engine, preferably diesel or lean burn gasoline, such as that of a vehicle. , a motor boat, a construction machine, or a locomotive, as well as for the treatment of gaseous effluents from all stationary installations emitting nitrogen oxides and sulfur oxides.
• the catalyst or the device according to the invention will then be arranged in the exhaust line, at a level where the temperature will be adequate for good activity.
• the present invention also relates to a process for preparing a catalyst as defined above comprising the following successive stages:
• step (ii) separating the compound obtained in step (i) above comprising a mixture of alumina, titanium oxide and silver, water, and drying the compound thus obtained,
• step (iii) heat treating the compound obtained in the preceding step (ii) comprising a mixture of alumina, titanium oxide and silver, to give the catalyst, and
• step (i) will advantageously be in powder form.
• Step (i) will preferably be carried out with stirring.
• the silver salt introduced into the aqueous solution will in particular be a salt of nitrate or of sulphate, and in particular a salt of nitrate.
• the titanium oxide may be obtained by introducing into the aqueous solution a titanium oxide mechanically mixed with alumina, or from a titanium salt such as titanium chloride, which hydrolyzes to the oxide of titanium. titanium with stirring in water.
• the water used will advantageously be a demineralized water whose conductivity is less than 14 ⁇ .
• the separation may be carried out by evaporation of the water, in particular under vacuum at a temperature of 60 ° C., or possibly by filtration.
• the drying will advantageously be carried out at a temperature of between 80 and 100 ° C.
• the catalyst thus obtained may also be subjected to hydrotreatment under a stream of air charged with water, for example containing 10% water, at a temperature of between 600 and 750 ° C.
• the method of preparation described above is an example is not limiting. We can also consider for example the preparation of such a catalyst by impregnation of silver from various precursors in various solvents, or by simple mechanical mixing of silver oxide, alumina and titanium oxide.
• the support may also be prepared by grafting ⁇ 2 from a flow of T1CI 4 passing through a bed of alumina, followed by hydrolysis.
• the present invention also relates to a method for preparing a device as defined above comprising the following successive steps:
• the slip contains 15 to 20% by weight of dry matter relative to the total weight of the slip, of which 70 to 90% by weight of the catalyst as defined above, advantageously 80%, and 10% to 30% by weight of binder, advantageously 20%, all being advantageously suspended in demineralized water.
• the binder in the sense of the present invention is a colloidal suspension to promote the adhesion of the catalyst on the monolith. This is for example an AI 2 O 3 pseudo-boehmite type.
• the present invention also relates to a process for reducing nitrogen oxides in a gaseous effluent also containing sulfur oxides, and preferably mainly S0 2 , by contacting said gaseous effluent with a catalyst as defined herein. above or a device as defined above in the presence of a reducing agent chosen from hydrocarbons, oxygenated compounds and their mixtures.
• Sulfur oxides mainly include sulfur dioxide
• the gaseous effluent to be treated in the context of this process may be in particular an exhaust gas from an engine, preferably diesel or lean burn gasoline.
• the hydrocarbons comprise in particular saturated or unsaturated hydrocarbon derivatives (that is to say comprising at least one double or triple bond) with a linear or branched chain, especially comprising 1 to 12 carbon atoms and mixtures thereof. It may be in particular ethylene, propylene, acetylene, decane, propane, dodecane and their mixtures.
• the oxygenated compounds include in particular alcohols, aldehydes and ketones.
• the alcohols consist of compounds comprising an OH function.
• R 1 represents a linear or branched hydrocarbon chain, saturated or unsaturated (preferably saturated), comprising in particular 1 to 6, of preferably 1 to 4, carbon atoms.
• R 1 represents a linear or branched hydrocarbon chain, saturated or unsaturated (preferably saturated), comprising in particular 1 to 6, of preferably 1 to 4, carbon atoms.
• R 1 represents a linear or branched hydrocarbon chain, saturated or unsaturated (preferably saturated), comprising in particular 1 to 6, of preferably 1 to 4, carbon atoms.
• R 1 represents a linear or branched hydrocarbon chain, saturated or unsaturated (preferably saturated), comprising in particular 1 to 6, of preferably 1 to 4, carbon atoms.
• It may especially be methanol, ethanol, n-propanol, isopropanol and their mixtures, including denatured ethanol and fuels containing ethanol such as for example the fuel E85.
• ethanol and more particularly ethanol denatured which may include
• denatured ethanol is understood to mean ethanol to which a denaturant is added to render the mixture unfit for consumption.
• denaturants mention may in particular be made of isopropanol.
• E85 fuel is a fuel containing between 70 and 85% by volume of ethanol.
• Aldehydes consist of compounds comprising a CHO function. In the context of the present invention, it will be in particular a compound of formula R 2 -CHO in which R 2 represents a linear or branched hydrocarbon chain, saturated or unsaturated (preferably saturated), including in particular 1 to 6, preferably 1 to 4, carbon atoms. This may include acetaldehyde.
• it will be in particular a compound of formula R3-C (O) -R 4 in which R 3 and R 4 each represent, independently of one another, a linear or branched hydrocarbon chain, saturated or unsaturated (preferably saturated), comprising especially 1 to 6, preferably 1 to 4, carbon atoms.
• This may include acetone.
• the oxygenated compound used in the context of this process may therefore be chosen from methanol, ethanol, n-propanol, isopropanol, acetaldehyde, acetone and their mixtures, including denatured ethanol and fuels. containing ethanol.
• the oxygenated compound will include ethanol and will be more particularly selected from denatured ethanol and E85 fuel.
• the ratio reducing agent on nitrogen oxide (C / NOx) will advantageously be between 2 and 10, especially between 2 and 6. This ratio corresponds to the number of moles of "carbon atoms of the reducing agent" (number of moles of reducing agent x number of carbon atoms contained in the reducing agent) over the number of moles of nitrogen oxide
• C / NOx ratio 2
• one mole of ethanol will be injected for 1 mole of nitrogen oxides.
• This process will also be advantageously carried out at a temperature of between 200 and 500 ° C., preferably between 300 and 450 ° C.
• the present invention also relates to a vehicle, a boat, a construction machine or a locomotive, comprising an engine, preferably Diesel or lean burn gasoline, and an exhaust line connected in output of the engine, characterized in that the catalyst or the device according to the invention is disposed in the exhaust line.
• an engine preferably Diesel or lean burn gasoline
• an exhaust line connected in output of the engine
• the catalyst or device according to the invention will then allow the treatment of the gases produced by the engine and containing oxides of nitrogen and oxides of sulfur.
• the present invention also relates to a stationary installation, such as for example a cogenerator or a household waste incinerator, producing a gaseous effluent containing nitrogen oxides and sulfur oxides and comprising a catalyst or a device according to the invention.
• the invention is arranged so as to allow the treatment of gaseous effluent (i.e. reduction of nitrogen oxides).
• Figures 1 to 6 show the conversion (in%) of ethanol (in black) and NOx (in gray) over time (in hours) under different catalyst conditions and composition of the gaseous effluent.
• the catalyst composition is 4% silver, on a support composed of 99.8% of alumina and 0.2% of titanium oxide.
• the catalyst was then coated on a cordierite honeycomb of 400 cpsi by several successive quenchings in a slip containing 20% of dry matter, of which 80% of the catalyst obtained previously and 20% of binder, the latter corresponding to to a colloidal alumina.
• the assembly was again calcined at 400 ° C. for 2 hours.
• honeycombs thus coated were placed in a crossed-bed fixed reactor, surrounded by thermo-regulated heating shells.
• the gaseous effluent at the reactor inlet has the following composition:
• the study was carried out at a constant temperature of 400 ° C and with a VVH of 30,000 h -1 .
• composition of the effluent at the outlet of the reactor was continuously monitored by different methods of analysis:
• the "holes" in the curves shown in the figures correspond to acquisition interruptions, in particular to perform a rinsing of the analyzers, or to redo the levels of water and ethanol.
• the study started with a C / NOx 3 ratio for 38 h, showing a decrease in initial activity of 80% (with 15 ppm S0 2 ) to about 65% (with 50 ppm S0 2 ) of conversion of NOx, activity that remains stable throughout the 38h.
• composition of the gaseous effluent * NOx: 1,200 ppm

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Citations (10)

• 2011
  • 2011-03-18 WO PCT/FR2011/050564 patent/WO2012127127A1/fr active Application Filing
  • 2011-03-18 BR BR112013023501A patent/BR112013023501A2/pt not_active Application Discontinuation

Patent Citations (11)

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