Exhaust gas purification system

An exhaust gas purification system configured to purify exhaust gas emitted from an internal combustion engine,

• the exhaust gas purification system comprising:
• an exhaust gas path through which exhaust gas flows;
• a first exhaust gas treatment section provided upstream in the exhaust gas path;
• and
• a second exhaust gas treatment section provided downstream in the exhaust gas path,
• wherein the first exhaust gas treatment section comprises:
• a flow-through type substrate;
• and
• first catalyst layers,
• wherein the flow-through type substrate comprises:
• cells each extending in the exhaust gas flow direction, and each having an open end on an exhaust gas inflow side thereof in the exhaust gas flow direction and an open end on an exhaust gas outflow side thereof in the exhaust gas flow direction;
• and
• a partition wall separating the cells from one another,
• wherein the first catalyst layers each comprise a portion that is formed on a surface of the partition wall,
• wherein the second exhaust gas treatment section comprises:
• a wall-flow type substrate;
• second catalyst layers;
• and
• third catalyst layers,
• wherein the wall-flow type substrate comprises:
• inflow-side cells each extending in the exhaust gas flow direction, and each having an open end on an exhaust gas inflow side thereof in the exhaust gas flow direction and a closed end on an exhaust gas outflow side thereof in the exhaust gas flow direction;
• outflow-side cells each extending in the exhaust gas flow direction, and each having a closed end on an exhaust gas inflow side thereof in the exhaust gas flow direction and an open end on an exhaust gas outflow side thereof in the exhaust gas flow direction;
• and
• a porous partition wall separating the inflow-side cells and the outflow- side cells from one another,
• wherein the second catalyst layers each have a portion that is formed on a surface on an inflow-side cell side of the partition wall, and extends from an end on an exhaust gas inflow side of the partition wall along the exhaust gas flow direction,
• wherein the third catalyst layers each have a portion that is formed on a surface on an outflow-side cell side of the partition wall, and extends from an end on an exhaust gas outflow side of the partition wall along a direction opposite to the exhaust gas flow direction,
• wherein the first catalyst layers each contain cerium element,
• wherein a percentage P1 of a mass of the cerium element contained in the first catalyst layers in terms of cerium oxide, to a mass of the first catalyst layers, is 5.0% by mass or more and 13.0% by mass or less,
• wherein the second catalyst layers each contain rhodium element,
• wherein the second catalyst layers and the third catalyst layers each contain cerium element, and
• wherein a percentage P23 of a total of a mass of the cerium element contained in the second catalyst layers in terms of cerium oxide, and a mass of the cerium element contained in the third catalyst layers in terms of cerium oxide, to a total of a mass of the second catalyst layers and a mass of the third catalyst layers, is 1.1 times or more and 5.3 times or less larger than the percentage P1.