Abstract: A process for removing nitrogen oxide from exhaust is disclosed, comprising contacting exhaust containing nitrogen oxide with an alumina catalyst which contains not more than 0.5% by weight of an alkali metal and/or an alkaline earth metal and has a total pore volume of from 0.48 to 1.2 cm.sup.3 .multidot.g.sup.-1 with 0.26 to 0.6 cm.sup.3 .multidot.g.sup.-1 of the total pore volume being formed of pores of not greater than 80 .ANG. or has a volume of pores formed of pores of not greater than 60 .ANG. of from 0.06 to 0.2 cm.sup.3 .multidot.g.sup.-l and which may have supported thereon tin in an oxidative atmosphere containing excess oxygen in the presence of a hydrocarbon or an oxygen-containing organic compound.

Abstract: A novel catalyst for catalytic reduction of nitrogen oxide using a hydrocarbon as a reducing agent is provided, which comprises (a) at least an element of the platinum group selected from the group consisting of platinum, iridium, rhodium and ruthenium and (b) gold, and which may further comprises (c) at least a metallic oxide selected from the group consisting of cerium oxide, lanthanum oxide, neodymium oxide, germanium oxide and gallium oxide.

Abstract: A catalyst for catalytic reduction of nitrogen oxide using at least one reducing agent selected from the group consisting of a hydrocarbon and an oxygen-containing organic compound is described, which includes an oxide represented by formula (V):A.sup.5.sub.x B.sup.3.sub.3-x C.sup.4.sub.3 O.sub.7 (V)wherein A.sup.5 represents at least one element selected from the group consisting of La, Y, Ce, Pr, Nd, Sm, Eu, and Gd; B.sup.3 represents at least one element selected from the group consisting of Ba, Sr, Ca, Mg, Pb, Zn, and Ag; C.sup.4 represents at least one element selected from the group consisting of Mn, Co, Fe, Ni, Cr, Cu, V, Mo, W, Ti, Zr, Nb, Pd, Rh, Ru, and Pt; and x is a number of from 0 to 1, supported on a solid acid carrier.

Abstract: A process for reducing nitrogen oxides to nitrogen from exhaust gases is disclosed, which involves bringing an exhaust gas containing nitrogen oxides into contact with at least one catalyst from proton-type zeolites, zeolites of an alkali metal exchanged form and acidic metal oxides, by reaction with a hydrocarbon or an oxygen-containing organic compound in an oxidizing atmosphere containing excess oxygen. A process which further involves bringing the exhaust gas into contact with an oxidizing catalyst subsequent to the above process.

Abstract: A process for removing nitrogen oxides from an exhaust gas by bringing the exhaust gas containing nitrogen oxides into contact with at least one catalyst selected from a polyvalent metal phosphate, a polyvalent metal sulfate or an aluminate of a transition metal of the 4th period of the Periodic Table in an oxidizing atmosphere containing excess oxygen and in the presence of a hydrocarbon or an oxygen containing organic compound. There is also disclosed a process for removing nitrogen oxides from an exhaust gas which comprises bringing the exhaust gas into contact with the above catalyst and then with an oxidation catalyst.