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
  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/061—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof containing metallic elements added to the zeolite
• • 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
  • B01D53/944—Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts
• • 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
  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/08—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the faujasite type, e.g. type X or Y
  • B01J29/16—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the faujasite type, e.g. type X or Y containing arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J29/166—Y-type faujasite
• • 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
  • B01J37/0246—Coatings comprising a zeolite
• • 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
  • F01N2370/00—Selection of materials for exhaust purification
  • F01N2370/02—Selection of materials for exhaust purification used in catalytic reactors
  • F01N2370/04—Zeolitic material
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B3/00—Engines characterised by air compression and subsequent fuel addition
  • F02B3/06—Engines characterised by air compression and subsequent fuel addition with compression ignition

Definitions

• This invention relates to the use of a catalyst for reducing the quantity and/or size of particulates in the exhaust gas of a diesel engine by means of a bifunctional catalyst containing a transition metal oxide and an acidic zeolite.
• a well-known measure widely used to prevent particulate emissions is to use filters.
• the disadvantage of filters lies in the danger of blockage by the particulates after a relatively short operating time. Accordingly, measures have to be taken to regenerate the particulate filters, for example by brief heating of the filters by suitable devices to the ignition temperature of the deposited particulates. Devices such as these are complicated and expensive and are not a practical solution, for example, for diesel-powered automobiles.
• the problem addressed by the present invention was further to reduce the quantity and/or size of the particulates.
• zeolite-containing catalysts which have acidic or cracking properties and which additionally contain oxides of the transition metals distinctly reduce the quantity and/or size of particulates in relation to the prior art without at the same time oxidizing the SO 2 in the exhaust gas to sulfates.
• the zeolite catalysts containing the added metal oxides have no oxidizing effect on the SO 2 in the exhaust gas, even at relatively high exhaust gas temperatures.
• the metal oxide addition also has a favorable effect on particulate reduction at relatively low temperatures so that particulate reduction is up to 50% greater than in the case of an acidic zeolite catalyst with no metal oxide addition.
• the present invention relates to the use of a catalyst for reducing the quantity and/or size of particulates in the exhaust gas of a diesel engine by means of a catalyst which is a combination of a zeolite having acidic properties and one or more transition metal oxides and/or oxides of the rare earths.
• Suitable metal oxide additions are, preferably, TiO 2 , V 2 O 5 , Cr 2 O 3 , MnO 2 , Fe 2 O 3 , CoO, NiO, CuO, Y 2 O 3 , ZrO 2 , Nb 2 O 5 , Ta 2 O 5 , WO 3 , MoO 3 , La 2 O 3 , Ce 2 O 3 , WO 3 , etc. or mixtures of these oxides.
• the oxides are preferably added in quantities of 0.1 to 20% by weight and, more preferably, in quantities of 0.5 to 10% by weight.
• Particularly suitable metal oxide additions are TiO 2 , V 2 O 5 , WO 3 , MoO 3 , La 2 O 3 and Ce 2 O 3 .
• the metal oxides are normally added to the zeolite.
• a binder is added so that the mixture may be adhesively applied to a support (for example of cordierite or of metal) or press-molded to form self-supporting shaped structures.
• the mixture is homogenized by intensive grinding, for example in stirred ball mills.
• the mixtures are then dried to a moisture content suitable for granulation and are press-molded to form shaped structures in suitable units, for example roller-type granulators, extruders.
• supports for example in the form of shaped structures or monolithic honeycombs, may also be coated with a suspension of the active components.
• the zeolite-containing catalysts may also be coated with salts of the transition metals or rare earths which may then be thermally decomposed.
• Zeolites particularly suitable for use in accordance with the invention include the following structure types: faujasites, pentasils, mordenites, ZSM 12, zeolite ⁇ , zeolite L, zeolite ⁇ , PSH-3, ZSM 22, ZSM 23, ZSM 48M EU-1, NU-86, offretith, ferrierite, etc.
• the pentasil type zeolite preferably has an SiO 2 to Al 2 O 3 ratio of 25 to 2000:1 and, more preferably 40 to 600:1.
• M 1 is an equivalent of an exchangeable cation
• n standing for the valency and the number corresponds to the charge equalization of M 2 ,
• M 2 is a trivalent element which, together with the Si, forms the oxidic skeleton of the zeolite,
• y/x is the SiO2/M 2 2 O 3 ratio
• q is the quantity of water adsorbed.
• zeolites are crystalline alumosilicates which are made up of a network of SiO 4 and M 2 O 4 tetrahedrons.
• the individual tetrahedrons are linked to one another by oxygen bridges over the corners of the tetrahedrons and form a three-dimensional network which is uniformly permeated by passages and voids.
• the individual zeolite structures differ in the arrangement and size of the passages and voids and in their composition.
• Exchangeable cations are incorporated to equalize the negative charge of the lattice arising out of the M2 component.
• the adsorbed water phase qH 2 O can be reversibly removed without the skeleton losing its structure.
• M 2 is often aluminium, but may be completely or partly replaced by certain other trivalent elements.
• zeolites A detailed account of zeolites can be found, for example, in D. W. Breck's book entitled “Zeolite Molecular Sieves, Structure, Chemistry and Use”, J. Wiley & Sons, New York, 1974. Another account, particularly of the zeolites relatively rich in SiO 2 which are of interest in catalytic applications, can be found in the book by P.A. Jacobs and J. A. Martens entitled “Synthesis of High-Silica Aluminosilicate Zeolites”, Studies in Surface Science and Catalysis, Vol. 33, Ed. B. Delmon and J. I. Yates, Elsevier, Amsterdam/Oxford/New York/Tokyo, 1987.
• M 2 stands for one or more elements from the group consisting of Al, B, Ga, In, Fe, Cr, V, As and Sb and, preferably, for one or more elements from the group consisting of Al, B, Ga and Fe.
• the zeolites mentioned may contain rare earths and/or protons as exchangeable cations M 1 .
• exchangeable cations are, for example, those of Mg, Ca, Sr, Ba, Zn, Cd and also transition metal cations such as, for example, Cr, Mn, Fe, Co, Ni, Cu, V, Nb, Mo, Ru, Rh, Pd, Ag, Ta, W, Re or Pt.
• preferred catalysts are those which contain zeolites of the structure types mentioned above, in which at least part, preferably 50 to 100% and, more preferably, 80 to 100% of all the metal cations originally present have been replaced by hydrogen ions, and which also contain the metal oxide additions.
• the acidic H forms of the zeolites are preferably produced by exchanging metal ions for ammonium ions and subsequently calcining the zeolite thus exchanged.
• zeolites of the faujasite type repetition of the exchange process and subsequent calcination under defined conditions lead to so-called ultrastable zeolites relatively poor in aluminium which are made thermally and hydrothermally more stable by this dealuminization process.
• Another method of obtaining zeolites of the faujasite type rich in SiO 2 is to subject the anhydrous zeolite to a controlled treatment with SiCl 4 at relatively high temperatures ( ⁇ 150° C.). As a result of this treatment, aluminium is removed and at the same time silicon is incorporated in the lattice. Under certain conditions, treatment with ammonium hexafluorosilicate also leads to a faujasite rich in SiO 2 .
• Another method of replacing/exchanging protons is to carry out the process with mineral acids in the case of zeolites which have a sufficiently high SiO 2 to Al 2 O 3 ratio (>5). Dealuminized zeolites can also be obtained in this way.
• SE zeolite Y rare-earth-exchanged acidic zeolite Y with an SiO 2 to Al 2 O 3 ratio of 4.9 and a degree of exchange of approx. 90% and containing 2% WO 3 , (based on the zeolite component.
• H zeolite Y dealuminized acidic zeolite Y with a molar SiO 2 to Al 2 O 3 ratio of 50 and an addition of 2% WO 3 , based on the zeolite.
• Engine Temp. at HC con- Particulate speed Pme manifold version conversion [r.p.m.] [bar] [0C] [%] [%] 2000 1 159 34.3 26.3 2000 6 425 29.5 36.1
• H zeolite Y dealuminized acidic zeolite Y with a molar SiO 2 to Al 2 O 3 ratio of 50 and an addition of 2% MoO 3 , based on the zeolite.
• Engine Temp. at HC con- Particulate speed Pme manifold version conversion [r.p.m.] [bar] [C] [%] [%] 2000 1 159 30.9 21.5 2000 6 425 26.7 34.8

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Health & Medical Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Analytical Chemistry (AREA)
• Environmental & Geological Engineering (AREA)
• Biomedical Technology (AREA)
• Combustion & Propulsion (AREA)
• Catalysts (AREA)
• Exhaust Gas Treatment By Means Of Catalyst (AREA)

Priority Applications (1)

Applications Claiming Priority (4)

Related Parent Applications (1)

Publications (1)

Family

ID=6465035

Family Applications (1)

Country Status (4)

Cited By (2)

Families Citing this family (9)

Citations (9)

Family Cites Families (5)

• 1992
  • 1992-08-07 DE DE4226112A patent/DE4226112B4/de not_active Expired - Fee Related
• 1993
  • 1993-08-03 JP JP5209967A patent/JPH06170173A/ja active Pending
  • 1993-08-06 FR FR9309737A patent/FR2694598B1/fr not_active Expired - Fee Related
• 2003
  • 2003-05-19 US US10/440,936 patent/US20030202926A1/en not_active Abandoned

Patent Citations (9)

Also Published As

Similar Documents

Legal Events