A method of reducing NO.sub.x in tail gas obtained during startup of a plant for preparing nitric acid may involve heating the tail gas from a starting temperature T.sub.0, through a threshold temperature T.sub.G, to an operating temperature T.sub.B at which steady-state operation of the plant can occur (T.sub.0<T.sub.G<T.sub.B). NO.sub.x-containing tail gas may be passed through a storage medium and at least partially stored while the temperature of the tail gas is lower than the threshold temperature T.sub.G. The NO.sub.x may be released, preferably when the temperature of the tail gas has attained the threshold temperature T.sub.G. The NO.sub.x may be combined with a reducing agent in the presence of an SCR catalyst after the temperature of the tail gas has exceeded the threshold temperature T.sub.G, but not before, resulting in catalytic reduction of at least a portion of the NO.sub.x.

A NO.sub.x absorber catalyst for treating an exhaust gas from a diesel engine. The NO.sub.x absorber catalyst comprises a first NO.sub.x absorber material comprising a molecular sieve catalyst, wherein the molecular sieve catalyst comprises a noble metal and a molecular sieve, and wherein the molecular sieve contains the noble metal; a second NO.sub.x absorber material comprising palladium (Pd) supported on an oxide of cerium; and a substrate having an inlet end and an outlet end.

An oxidation catalyst composite, methods, and systems for the treatment of exhaust gas emissions from a diesel engine are described. More particularly, an oxidation catalyst composite including a first washcoat comprising a zeolite, Pt, and first refractory metal oxide support containing manganese, a second washcoat comprising a second refractory metal oxide support, a Pt component and a Pd component, and a third washcoat comprising palladium and a rare earth oxide component is described.

A hydrocarbon and NOx catalyst trap includes a three-way catalyst, and a zeolite layer adjacent to the three-way catalyst and including alumina and silica arranged to form a repeating skeletal frame that defines cavities including active metal active sites for hydrocarbon and NOx trapping such that individual atoms of the active metal are bound to the frame within the cavities via oxygen atoms.

An apparatus is provided for treatment of process gas formed during nitric acid production by catalytic oxidation of NH.sub.3. The apparatus includes a reactor, a first catalyst bed for N.sub.2O decomposition, an absorption tower to react the NO.sub.x formed with an absorption medium downstream of the first catalyst bed, a device for adding NH.sub.3 added to tailgas entering the second catalyst bed, and a second catalyst bed for NO.sub.x reduction and further decrease in N.sub.2O in the tailgas exiting the absorption tower. The second catalyst bed contains at least one iron-loaded zeolite catalyst. N.sub.2O removal in the first catalyst bed is limited such that the process gas exiting the first catalyst bed exhibits a N.sub.2O content of >100 ppmv and a molar N.sub.2O/NO.sub.x ratio of >0.25. Treated gas exiting the second catalyst bed has a NO.sub.x concentration of <40 ppmv and a N.sub.2O concentration of <200 ppmv.

The present disclosure relates to a fuel filter (1) for filtering diesel fuel supplied to an internal combustion engine (2). The fuel filter (1) includes a filter element (12, 19) for trapping and decomposing precipitates suspended in the diesel fuel. An solid acid catalyst like a zeolite is provided for decomposing precipitates trapped by the filter element (12, 19). Sterol glycosides (precipitates) are splitted into sterol and glycoside moieties, which are soluble in the biodiesel, thus preventing clogging of the filter by sterol glycoside agglomerates. The sterol and glycoside moieties pass to the engine where they are burnt. The present disclosure also relates to a method of filtering diesel fuel for supply to an internal combustion engine (2).

An oxidation catalyst composite, methods, and systems for the treatment of exhaust gas emissions from a diesel engine are described. More particularly, an oxidation catalyst composite including a first washcoat comprising a zeolite, Pt, and first refractory metal oxide support containing manganese, a second washcoat comprising a second refractory metal oxide support, a Pt component and a Pd component, and a third washcoat comprising palladium and a rare earth oxide component is described.

The present invention relates to a catalyst comprising a carrier substrate of the length L extending between substrate ends a and b and a first washcoat zone, which comprises a) a zeolite, b) a redox active base metal compound and c) palladium in oxidic or metallic state which is fixed to the surface of a support oxide.

Disclosed is a reactive filter, that is a selective catalytic reduction filter or an oxidative reaction filter, including a porous substrate including internal pores having their inner surface, totally or partially, directly coated with a catalytic zeolite material resulting from an in situ hydrothermal synthesis. Also disclosed is a process for preparing such a reactive filter and the use thereof in an engine exhaust depolluting system.

The present disclosure describes hybrid binary catalysts (HBCs) that can be used as engine aftertreatment catalyst compositions, specifically 4-way catalyst compositions. The HBCs provide solutions to the challenges facing emissions control. In general, the HBCs include a porous primary catalyst and a secondary catalyst. The secondary catalyst partial coats the surfaces (e.g., the internal porous surface and/or the external surface) of the primary catalyst resulting in a hybridized composition. The synthesis of the HBCs can provide a primary catalyst whose entire surface, or portions thereof, can be coated with the secondary catalyst.