Abstract: An exhaust gas purification catalyst device includes a honeycomb base material and an inlet-side coat layer, wherein: the honeycomb base material includes a plurality of cells partitioned by porous partition walls, the plurality of cells including inlet-side cells and outlet-side cells and being configured such that exhaust gas that has flowed into the inlet-side cells passes through the partition walls and is exhausted from the outlet-side cells; and the inlet-side coat layer is present on the surface sides of the partition walls of the inlet-side cells, with the proportion of 4-9 ?m through-pores in the through-pore diameter distribution of the partition walls being at least 80 vol %, and the peak pore diameter measured using a mercury porosimeter being at least 3.0 ?m greater than the peak through-pore diameter measured using a perm porometer.

Abstract: An exhaust gas purification catalyst device includes a honeycomb base material and an inlet-side coat layer, wherein: the honeycomb base material includes a plurality of cells partitioned by porous partition walls, the plurality of cells including inlet-side cells and outlet-side cells and being configured such that exhaust gas that has flowed into the inlet-side cells passes through the partition walls and is exhausted from the outlet-side cells; and the inlet-side coat layer is present on the surface sides of the partition walls of the inlet-side cells, with the proportion of 4-9 ?m through-pores in the through-pore diameter distribution of the partition walls being at least 80 vol %, and the peak pore diameter measured using a mercury porosimeter being at least 3.0 ?m greater than the peak through-pore diameter measured using a perm porometer.

Abstract: The present invention is intended to improve a SOx reduction rate which is a ratio of an amount of SOx reduction with respect to an amount of SOx occlusion in SOx poisoning recovery processing. In the present invention, in the SOx poisoning recovery processing in which the SOx occluded in an NOx storage reduction catalyst is reduced by decreasing the air fuel ratio of an exhaust gas flowing into the NOx storage reduction catalyst to a predetermined air fuel ratio in a repeated manner, the length of a period in which the air fuel ratio of an exhaust gas flowing into the NOx storage reduction catalyst is decreased is made longer in a relatively early time during the processing than in a relatively late time during the processing.

Abstract: The present invention is intended to improve a SOx reduction rate which is a ratio of an amount of SOx reduction with respect to an amount of SOx occlusion in SOx poisoning recovery processing. In the present invention, in the SOx poisoning recovery processing in which the SOx occluded in an NOx storage reduction catalyst is reduced by decreasing the air fuel ratio of an exhaust gas flowing into the NOx storage reduction catalyst to a predetermined air fuel ratio in a repeated manner, the length of a period in which the air fuel ratio of an exhaust gas flowing into the NOx storage reduction catalyst is decreased is made longer in a relatively early time during the processing than in a relatively late time during the processing.