An exhaust gas purification filter that suppresses an increase in pressure loss associated with the formation of a catalyst layer and is excellent in PM burning quality. The exhaust gas purification filter includes a base and a catalyst layer provided on the base. The catalyst layer contains a carrier and a metal catalyst. Large pores having a circle equivalent diameter greater than 5 ?m occupy, when an area of the catalyst layer is 100% in an electron microscope observation image of a cross section of the catalyst layer, 45% or more of the area.

A ceramic porous body includes skeleton portions; and pore portions formed between the skeleton portions, the pore portions being capable of allowing a fluid to flow therethrough. In a cross section parallel to a flow direction of the fluid, the skeleton portions have a ratio of a skeleton length of 40 m or more of 15% or less in a direction orthogonal to the flow direction of the fluid.

A ceramic porous body comprising: skeleton portions including an aggregate and at least one binding material; and pore portions formed between the skeleton portions, the pore portions being capable of allowing a fluid to flow therethrough. In the ceramic porous body, the pore portions have a pore volume ratio of pores having a pore diameter of from 1 to 10 m, of 45% or more, and a ratio of a contact area between the aggregate and the binding material to a surface area of the binding material of from 20 to 60%.

A ceramic porous body comprising: skeleton portions; and pore portions formed between the skeleton portions, the pore portions being capable of allowing a fluid to flow therethrough. In the ceramic porous body, the pore portions satisfy the following equations (1) and (2) in a cross section parallel to a flow direction of the fluid;

L1/L20.92(1), and

L1+L227 m(2) in which L1 is an average length of the pore portions in the flow direction of the fluid; and L2 is an average length of the pore portions in a direction orthogonal to the flow direction of the fluid.

A honeycomb filter includes a pillar-shaped honeycomb structure body having a porous partition wall surrounding cells each of which has one end plugged by a plugging portion. An open frontal area O (%) of the cells in the honeycomb structure body is 75 to 80%, a porosity P (%) of the partition wall measured by a mercury press-in method is 52 to 58%, an average pore diameter D (m) of the partition wall measured by the mercury press-in method is 6 to 12 m, and a pore volume rate A (%) of pores whose pore diameters are not less than 20 m with respect to an overall pore volume of the partition wall is not more than 13.5%.

The honeycomb structure includes a pillar-shaped honeycomb structure body that includes a porous partition wall. When the thickness (m) of the partition wall is defined as T.sub.1 and, among pores formed in the partition wall, the value of an average pore diameter (m) of specific pores whose pore diameters measured by a mercury press-in method are 20 to 100 m is defined as D.sub.(20 to 100), T.sub.1/D.sub.(20 to 100) that is a value obtained by dividing T.sub.1 by D.sub.(20 to 100) is not less than 2.4, a ratio of a pore volume of the specific pores to an overall pore volume of the partition wall is 5 to 45%, and a ratio of a pore volume of large pores whose pore diameters are not less than 100 m to the overall pore volume of the partition wall is not more than 5%.

Provided is an exhaust purifying filter having high catalyst purification performance and particulate matter capturing performance while reducing pressure loss. A GPF includes a filter substrate in which a plurality of cells extending from an inflow-side end surface to an outflow-side end surface are partitioned and formed by a porous partition wall and an inflow-side cell in which an opening in the outflow-side end surface is sealed and an outflow-side cell in which an opening in the inflow-side end surface is sealed are alternately disposed; and a TWC which is carried on the partition wall, wherein a difference between a total volume of pores having pore diameters within a range of 0.1 m to 10.7 m in pore distribution of the GPF and a total volume of pores having pore diameters within a range of 0.1 m to 10.7 m in pore distribution of the filter substrate is 0.015 ml/g0.06 ml/g.

An exhaust purification system includes an LAF sensor provided in an exhaust pipe and generates a signal corresponding to an air-fuel ratio of exhaust gas. An upstream catalytic converter is downstream of the LAF sensor and has a catalyst to purify the exhaust gas. An O2 sensor is downstream of the upstream catalytic converter, and generates a signal corresponding to the air-fuel ratio of the exhaust gas. A GPF is downstream of a the O2 sensor and purifies the exhaust gas. An ECU controls an air-fuel mixture in an engine using output signal KACT of the LAF sensor and an output signal VO2 of the O2 sensor such that the air-fuel ratio of exhaust gas flowing into the GPF converges to a target value near the stoichiometric ratio. The GPF has a filter substrate and a downstream TWC supported by a partition of the filter substrate.

A honeycomb structure, including: a pillar-shaped honeycomb structure body having a first end face and a second end face and including a porous partition wall disposed so as to surround a plurality of cells, the plurality of cells extending from the first end face to the second end face and serving as a through channel of fluid, wherein the partition wall has a porosity of 45 to 65%, the partition wall has an average pore diameter of 15 to 25 m, and the partition wall has a cumulative pore volume, which is measured by mercury intrusion porosimetry, such that a pore volume ratio of pores having pore diameters of 10 m or less relative to the overall pore volume of the partition wall is 10% or less, and a pore volume ratio of pores having pore diameters of 40 m or more is 10% or less.

An exhaust treatment method and apparatus for treating an exhaust stream flowing through an exhaust line housing in a downstream direction, the apparatus comprising a first particulate filter, an SCR unit, and a second particulate filter downstream of the SCR unit, all serially positioned in the exhaust line.