A dual-layer catalyst includes a substrate, a first layer disposed on the substrate, and a second layer disposed on the first layer. The first layer includes a first catalyst for storing NO.sub.x when the first catalyst has a temperature below an active temperature of a second catalyst. The first catalyst is to release the stored NO.sub.x when the first catalyst is heated to the active temperature of the second catalyst. The second layer includes the second catalyst for ammonia Selective Catalytic Reduction of the released NO.sub.x. The dual-layer catalyst is to be included in a catalytic converter and a catalyst system for reducing NO.sub.x emissions from a diesel engine, the NO.sub.x emissions including NO.sub.x emitted during a predetermined cold-start time period.

The purpose of the present invention is to provide an exhaust purifier (1) which is capable of restoring a pressure difference (P) and a purification rate (NOx removal efficiency) of a NOx catalyst (14) to the initial states thereof. An exhaust purifier (1) for removing particulate matter adhered to a NOx catalyst (14) by injecting pressurized air using an air injection nozzle (16) into a housing (13) of a catalyst reactor (12) in Which the NOx catalyst (14) serving as a catalyst is positioned, wherein the particulate matter is removed by increasing the pressure inside the catalyst reactor (12) to a prescribed pressure (IP) within a prescribed interval of time (t) by operating an injection valve (17) for supplying pressurized air

The present invention provides for catalysts for selective catalytic reduction of nitrogen oxides. The catalysts comprise metal oxide supporters, vanadium, an active material, and antimony, a promoter that acts as a catalyst for reduction of nitrogen oxides, and at the same time, can promote higher sulfur poisoning resistance and low temperature catalytic activity. The amount of antimony of the catalysts is preferably 0.5-7 wt. %.

The invention provides processes for cleaning carbon dioxide-containing process gases from the preparation of vinyl acetate after reaction of ethylene with acetic acid and oxygen in heterogeneously catalyzed, continuous gas phase processes, characterized in that carbon dioxide-containing process gases, for removal of carbon dioxide, are contacted with one or more scrubbing solutions, and one or more scrubbing solutions comprise one or more oxides of metals (metal oxides) selected from the group comprising vanadium, niobium, tantalum, chromium, molybdenum, manganese and arsenic.

To be able to produce an SCR catalyst (2), in particular one having a zeolite fraction (Z) as catalytically active fraction, in a reliable process and at the same time achieve good catalytic activity of the catalyst (2), an inorganic binder fraction (B) which is catalytically inactive in the starting state and has been treated to develop catalytic activity is mixed into a catalyst composition (4). The inorganic binder component for the binder fraction (B) is, in the starting state, preferably porous particles (10), in particular diatomaceous earth, which display mesoporosity. To effect catalytic activation, the individual particles (10) are either coated with a catalytically active layer (12) or transformed into a catalytically active zeolite (14) with maintenance of the mesoporosity.

An ammonia slip control catalyst having a layer containing perovskite and a separate layer containing an SCR catalyst is described. The ammonia slip catalyst can have two stacked layers, with the top overlayer containing an SCR catalyst, and the bottom layer containing a perovskite. The ammonia slip catalyst can alternatively be arranged in sequential layers, with the SCR catalyst being upstream in the flow of exhaust gas relative to the perovskite. A system comprising the ammonia slip catalyst upstream of a PGM-containing ammonia oxidation catalyst and methods of using the system are described. The system allows for high ammonia oxidation with good nitrogen selectivity. Methods of making and using the ammonia slip catalyst to reduce ammonia slip and selectively convert ammonia to N.sub.2 are described.

In the plugged honeycomb structure, 30% or more of first intersection portions in which a first partition wall intersects a second partition wall are first specific intersection portions in which a diameter of a maximum inscribed circle drawn in the first intersection portion is a specific size for a shortest distance between an inflow cell and an outflow cell, and 30% or more of non-first intersection portions other than the first intersection portions are non-first specific intersection portions in which a diameter of a maximum inscribed circle drawn in a non-first intersection portion is a specific size for a shortest distance between the inflow cells or the outflow cells.

The present disclosure features a method of making an engine aftertreatment catalyst, where the engine aftertreatment catalyst includes a metal oxide, a metal zeolite, and/or vanadium oxide when the metal oxide is different from vanadium oxide, each of which can be independently surface-modified with a surface modifier. The method includes providing a solution including an organic solvent and an organometallic compound; mixing the solution with a metal oxide, a metal zeolite, and/or a vanadium oxide to provide a mixture; drying the mixture; and calcining the mixture to provide a surface-modified metal oxide catalyst, a surface-modified metal zeolite catalyst, and/or a surface-modified vanadium oxide catalyst. The organometallic compound can be, for example, a metal alkoxide, a metal carboxylate, a metal acetylacetonate, and/or a metal organic acid ester.

This disclosure features an exhaust aftertreatment system that includes a selective catalytic reduction catalyst that includes a metal oxide catalyst and a metal zeolite catalyst, a metal oxide catalyst that is other than a vanadium oxide catalyst and a vanadium oxide catalyst, or a metal oxide catalyst that is other than a vanadium oxide catalyst together with a metal zeolite catalyst and a vanadium oxide catalyst. When used in a selective catalytic reduction system in a diesel engine, the catalyst composition can increase a conversion efficiency of nitrogen oxides (NOx) to nitrogen and water by a minimum of 2 percent compared to the metal zeolite catalyst alone, the metal oxide catalyst alone, or the vanadium oxide catalyst alone, when present.

Catalytic cores for a wall-flow filter include juxtaposed channels extending longitudinally between an inlet side and an outlet side of the core, wherein the inlet channels are plugged at the outlet side and outlet channels are plugged at the inlet side. Longitudinal walls forming the inlet and outlet channels separate the inlet channels from the outlet channels. The walls include pores that create passages extending across a width of the walls from the inlet channels to the outlet channels. Catalysts are distributed across the width and length of the walls within internal surfaces of the pores in a manner such that the loading of each catalyst across the width varies by less than 50% from an average loading across the width.