摘要:
A low-oxygen content exhaust flow produced by an engine that is combusting, on average, a stoichiometric mixture of air and fuel generally contains various unwanted gaseous emissions. The exhaust flow is treated by an exhaust aftertreatment system that includes a three-way-catalyst (TWC) and an ammonia-selective catalytic reduction (ammonia-SCR) catalyst positioned downstream from the TWC in a flow direction of the exhaust flow. The ammonia-SCR catalyst includes (1) a base metal ion-substituted zeolite and/or a base metal ion-substituted silicoaluminophosphate and (2) an oxygen storage material selected from the group consisting of a metal oxide or a mixed metal oxide that exhibits oxygen storage and release capacity. The serial arrangement of the TWC and the ammonia-SCR catalyst enhances the conversion of NOX to N2 in the low oxygen-content exhaust flow produced by the engine and helps prevent ammonia slip to the atmosphere.
摘要:
A bi-functional catalyst material, a SCR converter that includes the bi-functional catalyst material, an exhaust aftertreatment system that includes the SCR converter, and a method for removing NOX contained in an exhaust flow produced by a lean-burn engine are disclosed. The bi-functional catalyst material can (1) oxidize NO to NO2 and (2) selectively reduce NOX to N2 when exposed to an exhaust mixture that comprises the exhaust flow from the lean-burn engine and a suitable reductant. The bi-functional catalyst material comprises metal oxide particles selected from the group consisting of perovskite oxide particles and manganese-based mixed metal oxide particles dispersed on a selective catalytic reduction (SCR) catalyst.
摘要:
An exhaust aftertreatment system and a method for treating exhaust produced by a lean-burn engine are provided. The exhaust aftertreatment system may include an exhaust gas treatment subsystem and a clean-up oxidation catalyst located downstream of the exhaust gas treatment subsystem. The clean-up oxidation catalyst can selectively oxidize NH3 to N2 in the hot, oxygen-abundant exhaust flow emanated from the lean-burn engine and passed through the exhaust gas treatment subsystem to help prevent ammonia slip to the atmosphere. The clean-up oxidation catalyst comprises perovskite oxide particles and/or manganese-containing mixed metal oxide particles dispersed on a selective catalytic reduction (SCR) catalyst.
摘要:
An after-treatment system architecture and method for oxidizing the nitric oxide component of an exhaust stream from a hydrocarbon fueled power source operated with a fuel lean combustion mixture.
摘要:
Following a cold start of a hydrocarbon-fueled engine operated in a lean-burn-combustion mode, several seconds and minutes may be required for the exhaust gas stream to heat exhaust treatment devices in the exhaust system and conduit to their effective operating temperatures. The warm-up period may be particularly long for a NOx reduction catalyst (SCR) located downstream in the exhaust flow system. Accordingly, a bed of absorbent material, such as a suitably sized bed of alumina particles, located upstream of the SCR, is used to temporarily absorb water and NOx from a relatively cold exhaust until the exhaust has suitably heated the SCR to its operating temperature. Then, the warmed exhaust will remove the water and NOx from their temporary storage material and carry them to the reduction catalyst.
摘要:
A method for monitoring performance of a passive selective catalytic reduction system includes operating the internal combustion engine in a preconditioning mode. Subsequent to the preconditioning, an air/fuel excursion is introduced into the exhaust gas feedstream and a signal output from a sensor monitoring the exhaust gas feedstream in the selective catalytic reduction system during the air/fuel excursion is monitored. An operating effectiveness is determined for the selective catalytic reduction system correlated to the signal output from the sensor monitoring the exhaust gas feedstream.
摘要:
One embodiment of the invention may include a method comprising providing a product comprising a substrate comprising a perovskite catalyst, NOx stored in or on the substrate and particulate matter in or on the substrate; releasing at least some of the stored NOx and oxidizing the released NOx to form NO2, and reacting the NO2 with carbon in the particulate matter to form at least one of CO or CO2.
摘要:
A method for removing NOX from an oxygen-rich exhaust flow produced by a combustion source that is combusting a lean mixture of air and fuel may include passing the oxygen-rich exhaust flow through an exhaust aftertreatment system that includes a NOX oxidation catalyst that includes perovskite oxide particles, a NOX storage catalyst, and a NOX reduction catalyst.
摘要:
One embodiment of the invention includes a method of treating a gas stream comprising flowing the gas stream over a hydrocarbon reduction and NOx reduction catalyst first, and thereafter flowing the gas over a perovskite and NOx trap material for NOx oxidation and storage. In one embodiment, the hydrocarbon reduction and NOx reduction catalyst may include palladium. In one embodiment, the perovskite catalyst may have the general formula ABO3, AA′BO3, ABB′O3, or AA′BB′O3. The perovskite catalyst may be the only catalyst or a second non-perovskite catalyst may include at least one of palladium, platinum, rhodium, ruthenium or a catalyst system including one or more of the same or alloys thereof. In one embodiment, the NOx trap material may include at least one of alkali metals, alkaline earth metals such as barium, calcium, potassium, or sodium.
摘要:
Precursor cations of A and B elements of an ABO3 perovskite in aqueous solution are formed as an ionic complex gel with citric acid or other suitable polybasic carboxylic acid. The aqueous gel is coated onto a desired catalyst substrate and calcined to form, in-situ, particles of the crystalline perovskite as, for example, an oxidation catalyst on the substrate. In one embodiment, a perovskite catalyst such as LaCoO3 is formed on catalyst supporting cell walls of an extruded ceramic monolith for oxidation of NO in the exhaust gas of a lean burn vehicle engine.