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 denitration catalyst for a high-temperature exhaust gas which is used to catalytically reduce and remove nitrogen oxides in the reaction temperature range of from 500.degree. to 700.degree. C. in the process of adding an ammonia gas to the exhaust gas containing the nitrogen oxides, the aforesaid catalyst being characterized by carrying 0.5 to 10% by weight of cerium in terms of Ce.sub.2 O.sub.3 or 0.5 to 5% by weight of iron in terms of Fe.sub.2 O.sub.3 on a high silica type zeolite in which the molar ratio of SiO.sub.2 /Al.sub.2 O.sub.3 is 20 or more.

Abstract: Disclosed is a catalyst for removing nitrogen oxides from exhaust gases from internal combustion devices such as boilers, gas turbine and diesel engines which is characterized in that the catalyst contains Component A comprising type II anhydrous gypsum (insoluble anhydrite) and Component B comprising titanium oxide, the sum of the weights of Components A and B is equal to or more than 80 weight % of the total weight of the catalyst, the weight ratio of Component B to (Component A+Component B) is between 0.05 and 0.3, and the catalyst contains at least one or more of the oxides of vanadium, tungsten, molybdenum, iron, copper, chromium and manganese.

Abstract: A catalyst for denitrizing nitrogen oxides contained in waste gas which contains a substantial amount of arsenic compounds therein, which comprises:(a) titanium, and(b) at least one element selected from the group consisting of arsenic and manganese. The catalyst is resistant to deactivation by arsenic compounds and retains high denitrizing activity over a long period of time. The catalyst may further contain at least one base metal selected from the group consisting of V, W, Mo, Cu, Fe, Cr, Co, Ni, Zn and Sn.

Abstract: A process for preparing a catalyst for removing nitrogen oxides which comprises sintering orthotitanic acid in coexistence of at least one compound, selected from silicic acid in the form of fine particles, tungsten compounds and molybdenum compounds.

Abstract: A method for recovering a denitrating catalyst for ammonia catalytic reduction which is characterized by treating the denitrating catalyst for ammonia catalytic reduction, in which a performance has deteriorated, with at least one selected from the group consisting of SO.sub.4.sup.2- compounds, sulfur compounds and sulfonic acid compounds in order to replenish the catalyst with a sulfur content.

Abstract: A method for recovering a denitrating catalyst which is characterized by washing, with an aqueous oxalic acid solution, the used tungsten-titania or the tungsten-titania-vanadium denitrating catalyst which dust components have adhered to or have accumulated on and in which an SO.sub.2 -oxidizing power has thus risen; impregnating the catalyst with a tungsten compound; and drying and calcining the thus treated catalyst.

Abstract: A catalyst for treating waste gases comprising nitrogen oxides, which catalyst comprises a protonized zeolite coating formed on the surface of a catalytic ingredient. This type of catalyst has a prolonged life and is very useful in treating waste gases comprising nitrogen oxides by adding ammonia to the waste gas and reducing the nitrogen oxides in the waste gas with the catalyst to render the nitrogen oxides non-noxious.