A catalytic article for treating an exhaust gas stream containing one or more of NOx, hydrocarbons, CO, SOx and ammonia from a combustion turbine comprises (a) a substrate having an inlet end and an outlet end defining an axial length; (b) an oxidation layer comprising an oxidation catalyst comprising one or more noble metals, the oxidation layer being positioned on the substrate and covering the axial length of the substrate; and (c) an SCR layer comprising an SCR catalyst, the SCR layer being positioned on the oxidation layer and overlapping a portion of the oxidation layer, wherein the portion is less than 100%.

An extruded honeycomb catalyst for nitrogen oxide reduction according to the selective catalytic reduction (SCR) method in exhaust gases from motor vehicles includes an extruded active carrier in honeycomb form having a first SCR catalytically active component and with a plurality of channels through which the exhaust gas flows during operation, and a washcoat coating having a second SCR catalytically active component being applied to the extruded body, wherein the first SCR catalytically active component and the second SCR catalytically active component are each independently one of: (i) vanadium catalyst with vanadium as catalytically active component; (ii) mixed-oxide catalyst with one or more oxides, in particular those of transition metals or lanthanides as catalytically active component; and (iii) an Fe- or a Cu-zeolite catalyst.

For purifying waste gas charged with nitrogen oxides in a reactor with heat-accumulator chambers containing heat-accumulator materials, the raw gas to be purified alternately enters one of the heat-accumulator chambers. Mixed with a reducing agent for the reduction of the nitrogen oxides, it is supplied to a catalyst for the reduction of the nitrogen oxides, and the clean gas heats the heat-accumulator material in the heat-accumulator chamber which the clean gas exits. A partial flow is taken therefrom, heated by means of a heat source and, mixed with a reducing agent, supplied again to the heat-accumulator chamber which the raw gas enters. This heated, recirculated gas forms the only heat source for the overall system.

A reducing agent injection device includes a first honeycomb structure and a urea spraying device spraying a urea water solution in mist form. A pair of electrode members is formed in the first honeycomb structure. The ratio L/D of length L in the cell extending direction of the honeycomb structure body to diameter D of the cross section perpendicular to the cell extending direction is 0.5 to 1.2. Also, it is preferable that a urea hydrolysis catalyzer is provided in the second end face side of the honeycomb structure body, with a gap from the second end face.

A catalyst for selective catalytic reduction is described. Cerium (III) sulfate (cerous sulfate) is bound to a support. The catalyst also includes vanadium oxide and cerium oxide.

A catalyst article for treating a flow of a combustion exhaust gas comprises: a catalytically active substrate comprising one or more channels extending along an axial length thereof through which, in use, a combustion exhaust gas flows, the one or more channels having a first surface for contacting a flow of combustion exhaust gas; wherein the substrate is formed of an extruded vanadium-containing SCR catalyst material, wherein a first layer is provided on at least a portion of said first surface, wherein the first layer comprises an ammonia slip catalyst composition comprising one or more platinum group metals supported on titania, a silica-titania mixed oxide, a CeZr mixed oxide, or a mixture thereof, and a second layer is provided on at least a portion of the first layer and comprises an SCR catalyst composition.

Method for reducing the content of nitrogen oxides NOx and nitrous oxide N2O in an input gas, comprising the steps of: treating said gas with a first amount of a NOx reducing agent in a first de-NOx catalytic bed; treating the effluent of said first de-NOx catalytic bed in at least one de-N2O catalytic bed for removal of N2O; treating the effluent of said at least one de-N2O catalytic bed with a second amount of a NOx reducing agent in a second de-NOx catalytic bed.

A catalyst for treating an exhaust gas comprising SO.sub.2, NO.sub.x and elemental mercury in the presence of a nitrogenous reductant comprises a composition containing oxides of: (i) Molybdenum (Mo) and optionally Tungsten (W); and (ii) Vanadium (V); and (iii) Titanium (Ti); and(iv) Phosphorus (P), wherein, with respect to the total metal atoms in the composition, the composition comprises: (i) Mo in an amount of less than 2 at. %, and optionally up to 9 at. % W; (ii) from 2.5 to 12 at. % V; (iii) from 85 to 96 at. % Ti, and wherein the composition comprises (iv) P in an atomic ratio to the sum of atoms of Mo, W and V of from 1:2 to 3:2. The values expressed must total 100%.

A catalyst for treating an exhaust gas comprising SO.sub.2, NO.sub.x and elemental mercury in the presence of a nitrogenous reductant comprises a composition containing oxides of: (i) Molybdenum (Mo) and/or Tungsten (W); (ii) Vanadium (V); (iii) Titanium (Ti), and (iv) an MFI zeolite, wherein the composition comprises, based on the total weight of the composition: (i) 1 to 6 wt % of MoO.sub.3 and/or 1 to 10 wt % WO.sub.3; and (ii) 0.1 to 3 wt % V.sub.2O.sub.5, and (iii) 48.5 to 94.5 wt % TiO.sub.2; and (iv) 35 to 50 wt % MFI zeolite.

A combustion system operated at low cost is provided. A combustion system 1 includes a combustion device 10 that burns fuel, an exhaust line L1 through which exhaust gas flows, the exhaust gas being generated through combustion of the fuel in the combustion device 10, an air preheater 30 that is disposed in the exhaust line L1 and that recovers heat from the exhaust gas, and a denitration device 40 that is disposed in the exhaust line L1 and that removes nitrogen oxide from the exhaust gas using a denitration catalyst. The denitration device 40 is disposed downstream from the air preheater 30 in the exhaust line L1, and the denitration catalyst contains 43 wt % or more of vanadium pentoxide and has a BET specific surface area of 30 m.sup.2/g or more.