The exhaust gas purification device includes: a substrate of wall flow structure having inlet cells, outlet cells and a porous partition wall; and a catalyst layer provided in at least part of internal pores of the partition wall and held on the surface of the internal pores. The relationship between an average filling factor A of the catalyst layer held in pores having a pore diameter of 5 m to less than 10 m, an average filling factor B of the catalyst layer held in pores having a pore diameter of 10 m to less than 20 m and an average filling factor C of the catalyst layer held in pores having a pore diameter of 20 m to less than 30 m, among the internal pores of the partition wall 16 in which the catalyst layer is held, satisfies the following expression: A<B<C.

A pillar-shaped honeycomb structure, comprising an outer peripheral side wall; first cells having an opening on the first end surface and having a sealing portion on the second end surface; and second cells adjacent to the first cells with partition walls interposed therebetween and having a sealing portion on the first end surface and having an opening on the second end surface; wherein the outer peripheral side wall, the partition walls, and the sealing portions are fired, and comprise cordierite as a main component and one or more sintering aids selected from ceria, zirconia, and titania; wherein in the partition walls, assuming an average porosity of a portion in a range A, and a portion in a range B is P.sub.1 (%); and assuming an average porosity of a portion in a range C is P.sub.2 (%), ?4?P.sub.1?P.sub.2?7 is satisfied.

A honeycomb filter includes a pillar-shaped honeycomb structure having a porous partition wall disposed so as to surround a plurality of cells which serve as a fluid through channel extending from a first end face to a second end face; and a plugging portion provided at either an end on the first end face side or the second end face side of the cell; wherein a thickness of the partition wall is 203 to 254 ?m, a porosity of the partition wall measured by the mercury press-in method is 55 to 70%, an average pore diameter of the partition wall measured by the mercury press-in method is 20 to 25 ?m, and the partition wall has an average base material neck diameter of 11 to 18 ?m for a base material neck part in which an actual part of a porous base material constituting the partition wall is locally narrowed.

Provided is an exhaust purification filter that is able to reduce pressure loss and that has high exhaust purification performance and particulate matter trapping performance. This exhaust purification filter comprises a filter substrate having a wall flow structure, and an exhaust purification catalyst supported on a partition wall of the filter substrate. The volume-based median pore diameter (D50) of the filter substrate is 18 ?m or greater, the full width at half maximum of the pore distribution of the filter substrate is 7 ?m to 15 ?m, and the exhaust purification catalyst is supported in an unevenly distributed manner in a high-density layer in which the density of the exhaust purification catalyst is relatively high and a low-density layer in which the density of the exhaust purification catalyst is relatively low.

A plugged honeycomb structure, including: a pillar-shaped honeycomb structure body including porous partition walls; and plugging portions disposed at open ends of cells at an inflow end face side or at an outflow end face side, wherein a pore diameter corresponding to the cumulative pore volume of 10% is D10, a pore diameter corresponding to the cumulative pore volume of 30% is D30, a pore diameter corresponding to the cumulative pore volume of 50% is D50, a pore diameter corresponding to the cumulative pore volume of 70% is D70, a pore diameter corresponding to the cumulative pore volume of 90% is D90, the pore diameter D10 is 6 m or more, the pore diameter D90 is 58 m or less, and the plugged honeycomb structure satisfies the relationship of Expression (1).

0.35(D70D30)/D501.5Expression (1):

A ceramic honeycomb structure having pluralities of flow paths partitioned by porous cell walls; (a) the cell walls having porosity of 50-60%; and (b) in a pore diameter distribution in the cell walls measured by mercury porosimetry, (i) pore diameters at cumulative pore volumes corresponding to particular percentages of the total pore volume being within specific ranges and having specific relationships; and (ii) the difference between a logarithm of the pore diameter at a cumulative pore volume corresponding to 20% of the total pore volume and a logarithm of the pore diameter at 80% being 0.39 or less, and its production method.

A ceramic honeycomb structure having pluralities of flow paths partitioned by porous cell walls; (a) the cell walls having porosity of 50-60%; and (b) in a pore diameter distribution in the cell walls measured by mercury porosimetry, (i) pore diameters at cumulative pore volumes corresponding to particular percentages of the total pore volume being within specific ranges and having specific relationships; and (ii) the difference between a logarithm of the pore diameter at a cumulative pore volume corresponding to 20% of the total pore volume and a logarithm of the pore diameter at 80% being 0.39 or less, and its production method.

A plugged honeycomb structure includes: a pillar-shaped honeycomb substrate having a partition wall base material that defines a plurality of cells serving as a through channel of fluid; a plugging portion disposed at open ends of predetermined cells at an inflow-side end face of fluid and at open ends of residual cells at an outflow-side end face of fluid; and a porous trapping layer disposed at least at a surface of the partition wall base material of the residual cells. The partition wall base material is formed by a base material porous body including cordierite as a main phase, the trapping layer is formed by a trapping layer porous body including cordierite as a main phase, and a part of the trapping layer penetrating into pores formed at the partition wall base material has a thickness of 0 to 20 m.

A plugged honeycomb structure including: a pillar-shaped honeycomb structure body having porous partition walls made of a material including silicon carbide, and plugging portions, wherein a porosity of the partition walls is from 42 to 52%, a thickness of the partition walls is from 0.15 to 0.36 mm, a ratio of a volume of pores having pore diameters of 10 m or less to a total pore volume of the partition walls is 41% or less, a ratio of a volume of pores having pore diameters in a range of 18 to 36 m to the total pore volume is 10% or less, the pore diameter indicating a maximum value of the log differential pore volume is in a range of 10 to 16 m, and a half-value width of a peak including the maximum value of the log differential pore volume is 5 m or less.

A plugged honeycomb structure including: a pillar-shaped honeycomb structure body having porous partition walls made of a material including silicon carbide, and plugging portions, wherein a porosity of the partition walls is from 42 to 52%, a thickness of the partition walls is from 0.15 to 0.36 mm, a ratio of a volume of pores having pore diameters of 10 m or less to a total pore volume of the partition walls is 41% or less, a ratio of a volume of pores having pore diameters in a range of 18 to 36 m to the total pore volume is 10% or less, the pore diameter indicating a maximum value of the log differential pore volume is in a range of 10 to 16 m, and a half-value width of a peak including the maximum value of the log differential pore volume is 5 m or less.