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Assigneedmc2 Degussa Metals Catalysts Cerdec AG
InventorsRainer Domesle, Harald Klein, Thomas Kreuzer, Egbert Lox
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A catalyst for purifying the exhaust gases of diesel engines, which catalyst contains at least one zeolite and, additionally, at least one of the support oxides aluminum oxide, silicon dioxide, titanium dioxide and aluminum silicate and at least one of the noble metals platinum, palladium, rhodium and iridium. In this catalyst the atoms of the noble metals have a mean oxidation number of less than +2.5, on average more than 3 metal ligands and less than 3 oxygen ligands and are present on the zeolites and support oxides in the form of crystallites having a mean particle size of from 1 to 6 nm.
A catalyst for purifying the exhaust gases of a diesel engine, comprising a support material containing at least one zeolite and, additionally, at least one of the support oxides selected from the group consisting of aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide and aluminum silicate and mixed oxides thereof and at least one of the noble metals selected from the group consisting of platinum, palladium, rhodium, iridium, gold and silver, wherein atoms of the noble metals present in said catalyst have a mean oxidation number of less than +2.5, on average more than 3 metal ligands and less than 3 oxygen ligands and are present on the zeolite and support oxides in the form of crystallites having a mean particle size of from 1 to 6 nm.
A monolithic honeycomb carrier for purifying the exhaust gases of a diesel engine, comprising an inert ceramic or metal carrier in the shape of a honeycomb having flow channels defined by the walls of the honeycomb, through which the exhaust gas passes, said walls having deposited on at least some surfaces thereof a support material containing at least one zeolite and, additionally, at least one of the support oxides selected from the group consisting of aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide and aluminum silicate and mixed oxides thereof and at least one of the noble metals selected from the group consisting of platinum, palladium, rhodium, iridium, gold and silver, wherein atoms of the noble metals present in said catalyst have a mean oxidation number of less than +2.5, on average more than 3 metal ligands and less than 3 oxygen ligands and are present on the zeolite and support oxides in the form of crystallites having a mean particle size of from 1 to 6 nm.
An exhaust purification system for purifying the exhaust gases of diesel engines, comprising an inert honeycomb carrier having deposited on internal surfaces thereof a catalyst containing at least one zeolite and, additionally, at least one of the support oxides selected from the group consisting of aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide and aluminum silicate and mixed oxides thereof and at least one of the noble metals selected from the group consisting of platinum, palladium, rhodium, iridium, gold and silver, wherein atoms of the noble metals present in said catalyst have a mean oxidation number of less than +2.5, on average more than 3 metal ligands and less than 3 oxygen ligands and are present on the zeolite and support oxides in the form of crystallites having a mean particle size from 1 to 6 nm.
A catalyst for purifying the exhaust gases of a diesel engine, comprising a support material containing at least one zeolite and, additionally, at least one of the support oxides selected from the group consisting of aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide and aluminum silicate and mixed oxides thereof and at least one of the noble metals selected from the group consisting of platinum, palladium, rhodium, iridium, gold and silver, wherein atoms of the noble metals present in said catalyst have a mean oxidation number of less than +2.5, on average more than 3 metal ligands and less than 3 oxygen ligands and are present on the zeolite and support oxides in the form of crystallites having a mean particle size from 1 to 6 nm made by a process wherein said support oxides and the zeolites are first impregnated separately with precursor compounds of the noble metals, and then calcined in the still moist state in the course of from 0.1 to 10 seconds by being blown into combustion waste gases at a temperature of from 500 to 1000° C., and are then processed to a common coating dispersion with which a monolithic honeycomb body is subsequently coated, and the coating is then dried, calcined and, finally, reduced.
A catalyst for purifying the exhaust gases of a diesel engine, comprising a support material containing at least one zeolite and, additionally, at least one of the support oxides selected from the group consisting of aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide and aluminum silicate and mixed oxides thereof and at least one of the noble metals selected from the group consisting of platinum, palladium, rhodium, iridium, gold and silver, wherein the weight ratio of the support oxides to the zeolite is from 10:1 to 2:1 and the mass ratio of the noble metals deposited on the zeolites to the noble metals deposited on the support oxides in the catalyst is from 1:100 to 1:10.
Dependencies are inferred from the claim text.
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Containing iron group metals, noble metals or copper: noble metals
By catalytic processes: simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts
Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]:…
Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium: silica…
Term ended 15 Jan 2022 (estimated)
The present invention relates to a catalyst for purifying the exhaust gases of diesel engines, which catalyst contains at least one zeolite and, additionally, at least one support oxide selected from the group consisting of aluminum oxide, silicon dioxide, titanium dioxide and aluminum silicate and at least one noble metal selected from the group consisting of platinum, palladium, rhodium, iridium, gold and silver.
The exhaust gas of diesel engines contains carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NOx), sulfur dioxide (SO2) and carbon black particles as atmospheric pollutants. The unburned hydrocarbons include paraffins, olefins, aldehydes and aromatic compounds. In comparison with the exhaust gases of gasoline engines, diesel exhaust gases contain a substantially higher proportion of not readily oxidizable, long-chained paraffins, which are for a large part condensed onto the carbon black particles as so-called VOF's (VOF=volatile organic fraction) and hence increase the particulate load of the exhaust gas. The sulfur dioxide contained in the exhaust gas originates from the sulfur content of the diesel fuel. By oxidation to sulfur trioxide, sulfates may form which likewise accumulate on the carbon black particles and increase the mass of the particles.
Moreover, diesel exhaust gases are leaner than stoichiometric in composition, which means that their oxygen content is higher than would be necessary for complete combustion of all combustible constituents of the exhaust gas. The oxygen concentration in diesel exhaust gas is usually from 3 to 10 vol. %, whereas in stoichiometrically composed exhaust gases of gasoline engines it is only about 0.7 vol. %.
A catalyst consisting of a mixture of two platinum-catalyzed powders was prepared.
For the preparation of powder 1, 1 kg of an aluminum silicate (5 wt. % silicon dioxide; specific surface area: 153 m2/g) was placed in a dragée-making vessel. The aluminum silicate had a water absorption capacity of 800 ml/kg. While continuously being circulated, the aluminum silicate was sprayed with 766 ml of an aqueous solution of ethanolamineplatinum(IV) hexahydroxide ((EA)2Pt(OH)6═(HO—C2H4—NH3)2+PtIV(OH)6) at a volume flow rate of 56 ml/(kg.min). The still pourable, moist powder was calcined by being blown into a hot stream of gas, produced by methane combustion, at a gas temperature of 780° C. and with a dwell time in the stream of gas of about one second (spray calcination).
The Pt-aluminum silicate powder (powder 1) so prepared had a platinum content of 2.79 wt. %.