초록

S is aluminum or silicon-containing support, and is zeolite, silica, alumina or silica-alumina.

대표청구항 ▼

[ What is claimed is:] [1.] A catalyst for reduction of nitrogen oxides represented by the formula P (A.sub.a O.sub.x.B.sub.b O.sub.y).Q(C.sub.c O.sub.z.C'.sub.c' O.sub.z')/S comprising mixed metal oxides represented by the formula P(A.sub.a O.sub.x.B.sub.b O.sub.y).Q(C.sub.c O.sub.z.C'.sub.c' O.sub

[ What is claimed is:] [1.] A catalyst for reduction of nitrogen oxides represented by the formula P (A.sub.a O.sub.x.B.sub.b O.sub.y).Q(C.sub.c O.sub.z.C'.sub.c' O.sub.z')/S comprising mixed metal oxides represented by the formula P(A.sub.a O.sub.x.B.sub.b O.sub.y).Q(C.sub.c O.sub.z.C'.sub.c' O.sub.z') in an amorphous state supported on a zeolite whereinA and B are different metals selected from the group consisting of lanthanide metals, alkali metals and alkaline earth metals, with the proviso that at least one of A and B is a lanthanide metal, and when A is a lanthanide metal, a is not zero and when B is a lanthanide metal, b is not zero,C and C' are metals selected from the group consisting of transition metals of the first transition period of the periodic table, silver, platinum, rhodium, iridium, ruthenium, rhenium, and palladium,a, b, c and c' are numbers ranging from 0 to 1, provided that a+b=1, c+c'=1,x, y, z and z' are numbers chosen to satisfy the valence requirements of A, B, C and C',P and Q are numbers chosen so that the ratio P:Q is 1:1, and S is a zeolite support;wherein said catalyst is produced by supporting said mixed metal oxides represented by the formula P(A.sub.a O.sub.x.B.sub.b O.sub.y).Q(C.sub.c O.sub.z.C'.sub.c' O.sub.z') in an amorphous state on a zeolite by calcining precursors of said metal oxides mixed with said zeolite support material in a mole ratio of said precursors to said support material of 0.01:1 to 5:1 at a temperature of 400.degree. C. to 700.degree. C. [5.] A method for removing nitrogen oxides from exhaust gases of combustion containing 0.1% to 20% excess oxygen by selective catalytic reduction which comprises contacting said exhaust gas over a catalyst comprising P(A.sub.a O.sub.x.B.sub.b O.sub.y).Q(C.sub.c O.sub.z.C'.sub.c' O.sub.z')/S in the presence of 100 to 100,000 ppm of a reducing agent comprising a hydrocarbon having 1 to 5 carbon atoms at a temperature of 200.degree. to 800.degree. C., a pressure of 1 to 10 atmospheres, a space velocity of 1000 to 100,000/hour, whereinA and B are different metals selected from the group consisting of lanthanide metals, alkali metals and alkaline earth metals, with the proviso that at least one of A and B is a lanthanide metal, and when A is a lanthanide metal, a is not zero and when B is a lanthanide metal, b is not zero,C and C' are metals selected from the group consisting of transition metals of the first transition period of the periodic table, silver, platinum, rhodium, iridium, ruthenium, rhenium, and palladium,a, b, c and c' are numbers ranging from 0 to 1, provided that a+b=1, c+c'=1,x, y, z and z' are numbers chosen to satisfy the valence requirements of A, B, C and C',P and Q are numbers chosen so that the ratio P:Q is 1:1, and S is a zeolite support;wherein said catalyst is produced by supporting said mixed metal oxides represented by the formula P(A.sub.a O.sub.x.B.sub.b O.sub.y).Q(C.sub.c O.sub.z.C'.sub.c' O.sub.z') in an amorphous state on a zeolite by calcining precursors of said metal oxides mixed with said zeolite support material in a mole ratio of said precursors to said support material of 0.01:1 to 5:1 at a temperature of 400.degree. C. to 700.degree. C.