Abstract: A method of denitrating an exhaust gas by means of removing nitrogen oxides catalytically using ammonia as a reducing agent while introducing an exhaust gas containing the nitrogen oxides into a reaction vessel packed with a catalyst, comprising:providing a denitration catalyst layer in the upstream of the gas flow, an ammonia decomposition catalyst layer capable of decomposing oxidatively ammonia into nitrogen and nitrogen oxides in the downstream and a second denitration catalyst layer or a denitration catalyst layer capable of decomposing ammonia in the further downstream; and,adding ammonia in an amount not less than the reaction equivalence for the nitrogen oxides in the exhaust gas to the inlet of the first denitration catalyst layer.

Abstract: Disclosed are (1) a method for the regeneration of a denitration catalyst wherein, in order to regenerate a denitration catalyst having reduced denitration power, the catalyst is cleaned with a cleaning fluid having a hydrofluoric acid concentration of 0.3 to 3% by weight and maintained at a temperature of 20 to 80.degree. C., and (2) a method for the regeneration of a denitration catalyst which comprises the steps of cleaning a denitration catalyst having reduced denitration power under the conditions described in (1) above, drying the cleaned catalyst, and impregnating the catalyst with a catalytically active component so as to support it on the catalyst.

Abstract: A catalyst for cleaning exhaust gases has a first catalyst layer having as an active metal on an elemental support at least one noble metal selected from the group consisting of platinum, rhodium and palladium and a second catalyst layer having iridium as an active metal which is provided as a overlayer on the first catalyst layer.

Abstract: A method of denitrating an exhaust gas by means of removing nitrogen oxides catalytically using ammonia as a reducing agent while introducing an exhaust gas containing the nitrogen oxides into a reaction vessel packed with a catalyst, comprising:providing a denitration catalyst layer in the upstream of the gas flow, an ammonia decomposition catalyst layer capable of decomposing oxidatively ammonia into nitrogen and nitrogen oxides in the downstream and a second denitration catalyst layer or a denitration catalyst layer capable of decomposing ammonia in the further downstream; and,adding ammonia in an amount not less than the reaction equivalence for the nitrogen oxides in the exhaust gas to the inlet of the first denitration catalyst layer.

Abstract: A catalyst for cleaning exhaust gases has a first catalyst layer having as an active metal on an elemental support at least one noble metal selected from the group consisting of platinum, rhodium and palladium and a second catalyst layer having iridium as an active metal which is provided as a overlayer on the first catalyst layer.

Abstract: An ammonia decomposition catalyst wherein a first catalyst having a crystalline silicate which is represented by the formula in terms of molar ratio of oxides as dehydrated:(1.+-.0.8)R.sub.2 O.?aM.sub.2 O.sub.3.bM'O.cAl.sub.2 O.sub.3 !.ySiO.sub.2,wherein R denotes an alkaline metal ion and/or hydrogen ion, M denotes a VIII Group element, rare earth element, titanium, vanadium, chromium, niobium, antimony or gallium, M' denotes magnesium, calcium, strontium or barium, a.gtoreq.0, 20>b.gtoreq.0, a+c=1, 3000>y>11 or a specific porous material as a carrier and iridium or a noble metal as an active metal is present together with or covered with a second catalyst having at least one element selected from the group consisting of titanium, vanadium, tungsten and molybdenum, if necessary, as well as a method of using the same.

Abstract: A method for recovering an ammonia adsorbent which comprises streaming an NO.sub.x -containing gas at 300.degree.-600.degree. C. through an ammonia adsorbent layer which adsorbs ammonia and which is saturated with ammonia.

Abstract: A method for treating ammonia in an exhaust gas on the downstream side of a dry denitration device using ammonia as a reducing agent comprises the step of alternately carrying out ammonia adsorption and ammonia desorption/decomposition to continuously treat ammonia in the exhaust gas in a plurality of constitutional units parallelly connected on an exhaust gas line, the aforesaid constitutional units being constituted so as to carry out the steps of adsorbing/removing ammonia in an ammonia adsorbent-filling tower disposed at a position, where an exhaust gas temperature is 200.degree. C. or less, on the downstream side of the dry denitration device; heating, up to a temperature of 300.degree. C. or more, the ammonia adsorbent-filling tower on which ammonia is adsorbed in a saturated state, to desorb ammonia; and decomposing ammonia in an ammonia decomposition catalyst-filling tower disposed on a desorption ammonia gas line.

Abstract: A method for the denitration of exhaust gas from a gas turbine or an internal combustion engine which comprises (a) reducing a part of the NO.sub.2 constituting NO.sub.x contained in the exhaust gas to NO by means of a reduction catalyst bed for reducing NO.sub.2 to NO, the reduction catalyst bed being installed in flow communication with the exhaust gas outlet of the gas turbine or internal combustion engine, and (b) injecting NH.sub.3 into the exhaust gas within an exhaust heat recovery unit and then decomposing and removing NO.sub.x contained in the exhaust gas and now composed chiefly of NO, by means a denitration catalyst bed installed within the exhaust heat recovery unit to effect the catalytic reduction of NO.sub.x with NH.sub.3.

Abstract: An ammonia decomposition catalyst wherein a first catalyst having a crystalline silicate which is represented by the formula in terms of molar ratio of oxides as dehydrated: (1±0.8)R2O.[aM2O3.bM?O.cAl2O3].ySiO2, wherein R denotes an alkaline metal ion and/or hydrogen ion, M denotes a VIII Group element, rare earth element, titanium, vanadium, chromium, niobium, antimony or gallium, M? denotes magnesium, calcium, strontium or barium, a?0, 20>b?0, a+c=1, 3000>y>11 or a specific porous material as a carrier and iridium or a noble metal as an active metal is present together with or covered with a second catalyst having at least one element selected from the group consisting of titanium, vanadium, tungsten and molybdenum, if necessary, as well as a method of using the same.