Catalyst for purifying oxygen rich exhaust gas

A catalyst for purifying an exhaust gas, said catalyst comprising:

• a substrate;
• and
• a catalytic coating formed on said substrate, said catalytic coating comprising:
• a first grain including a porous carrier which supports thereon at least one first noble metal selected from the group consisting of platinum, palladium, rhodium and iridium;
• and
• a second grain including a first double oxide represented by the following general formula (1);
• (La.sub.1-x A.sub.x).sub.1-.alpha. BZr.sub..beta. O.sub..delta.( 1)
• where A is at least one element selected from the group consisting of barium, potassium and cesium, B is at least one transition element selected from the group consisting of iron, cobalt, nickel and manganese, x is a number which is greater than 0 and less than 1, .alpha. is a number which is greater than 0 and less than 0.2, .beta. is a number which is greater than 0 and less than 3, and .delta. is a number which is greater than zero.

A method of producing a catalyst used for purifying an exhaust gas, said catalyst comprising a substrate and a catalytic coating formed on said substrate, said method comprising the following steps of:

• (a) preparing a mixture comprising:
• a first powder including a porous carrier which supports thereon at least one first noble metal selected from the group consisting of palladium and rhodium;
• and
• a second powder including a first double oxide which supports thereon at least one second noble metal selected from the group consisting of platinum and palladium, said first double oxide being represented by the following general formula (1):
• (La.sub.1-x A.sub.x).sub.1-.alpha. BO.sub..delta. ( 1)
• where A is at least one element selected from the group consisting of barium, potassium and cesium, B is at least one transition element selected from the group consisting of iron, cobalt, nickel and manganese, x is a number which is greater than 0 and less than 1, .alpha. is a number which is greater than 0 and less than 0.2, and .delta. is a number which is greater than zero, wherein said first double oxide further comprises zirconium;
• (b) preparing a slurry by adding water to said mixture;
• (c) applying said slurry to said substrate, such that a precursor of said catalytic coating is formed on said substrate;
• and
• (d) baking said precursor into said catalytic coating.

A method of producing a catalyst used for purifying an exhaust gas, said catalyst comprising a substrate and a catalytic coating formed on said substrate, said method comprising the following steps of:

• (a) preparing a mixture comprising:
• a first powder including a porous carrier which supports thereon at least one first noble metal selected from the group consisting of platinum, palladium, rhodium and iridium;
• and
• a second powder including a first double oxide represented by the following general formula (1):
• (La.sub.1-x A.sub.2).sub.1-.alpha. BZr.sub..beta. O.sub..delta.( 1)
• where A is at least one element selected from the group consisting of barium, potassium and cesium, B is at least one transition element selected from the group consisting of iron, cobalt, nickel and manganese, x is a number which is greater than 0 and less than 1, .alpha. is a number which is greater than 0 and less than 0.2, .beta. is a number which is greater than 0 and less than 3, and .delta. is a number which is greater than zero;
• (b) preparing a slurry by adding water to said mixture;
• (c) applying said slurry to said substrate, such that a precursor of said catalytic coating is formed on said substrate;
• and
• (d) baking said precursor into said catalytic coating.

A catalyst for purifying an exhaust gas, said catalyst comprising:

• a substrate;
• and
• a catalytic coating formed on said substrate, said catalytic coating comprising:
• a first grain including a porous carrier which supports thereon at least one first noble metal selected from the group consisting of palladium and rhodium;
• a second grain including a first double oxide which supports thereon at least one second noble metal selected from the group consisting of platinum and palladium, said first double oxide being represented by the following general formula (1);
• (La.sub.1-x A.sub.x).sub.1-.alpha. BO.sub..delta. ( 1)
• where A is at least one element selected from the group consisting of barium, potassium and cesium, B is at least one transition element selected from the group consisting of iron, cobalt, nickel and manganese, x is a number which is greater than 0 and less than 1, .alpha. is a number which is greater than 0 and less than 0.2, and .delta. is a number which is greater than zero;
• and
• a third grain including a second double oxide containing cerium and zirconium.

A method of producing a catalyst used for purifying an exhaust gas, said catalyst comprising a substrate and a catalytic coating formed on said substrate, said method comprising the following steps of:

• (a) preparing a mixture comprising:
• a first powder including a porous carrier which supports thereon at least one first noble metal selected from the group consisting of palladium and rhodium;
• a second powder including a first double oxide which supports thereon at least one second noble metal selected from the group consisting of platinum and palladium, said first double oxide being represented by the following general formula (1):
• (La.sub.1-x A.sub.x).sub.1-.alpha. BO.sub..delta. ( 1)
• where A is at least one element selected from the group consisting of barium, potassium and cesium, B is at least one transition element selected from the group consisting of iron, cobalt, nickel and manganese, x is a number which is greater than 0 and less than 0.2, .beta. is a number which is greater than 0 and less than 3, and .delta. is a number which is greater than zero;
• and
• a third grain including a second double oxide comprising cerium and zirconium;
• (b) preparing a slurry by adding water to said mixture;
• (c) applying said slurry to said substrate, such that a precursor of said catalytic coating is formed on said substrate;
• and
• (d) baking said precursor into said catalytic coating.