A honeycomb structure body is constituted of a circumferential region including the outermost circumference in a cross section of the honeycomb structure body which is perpendicular to an extending direction of cells, and a central region excluding the circumferential region. The circumferential region includes a specific circumferential region in which pressure loss with soot when an amount of the deposited soot is 4 g/L is higher than the pressure loss with soot of the central region as much as 15% or more and in which an open frontal area of the circumferential region is the same as or larger than an open frontal area of the central region. In the cross section of the honeycomb structure body, a ratio of an area of the specific circumferential region is 5% or more to a total area of the circumferential region and the central region.

A plugged honeycomb structure includes a plurality of honeycomb segments, a bonding layer, and plugging portions plugging open ends of cells of the honeycomb segments. The honeycomb segments include circumferential segments and central segments. The circumferential segments include at least one specific circumferential segment in which pressure loss with soot when an amount of the deposited soot is 4 g/L is higher than the pressure loss with soot of the central segment as much as 15% or more and in which an open frontal area of the circumferential segment is the same as or larger than an open frontal area of the central segment. In a cross section of a honeycomb structure body which is perpendicular to an extending direction of the cells, a ratio of an area of the specific circumferential segment is 4% or more to a total area of the circumferential segments and the central segments.

A plugged honeycomb structure includes a honeycomb structure body having a porous partition wall disposed to surround a plurality of cells; and a plugging portion disposed at one end of the cells, wherein, in a section orthogonal to the extending direction of the cell, the cells each have a shape that is polygon, and one of the inflow cells and another are adjacent to each other with the partition wall therebetween, and in the section orthogonal to the extending direction of the cell, a total area of the inflow cell is larger than a total area of the outflow cell, a porosity of the partition wall is 38% or more, a thickness of the partition wall is 125 m or more and 280 m or less, a cell density of the honeycomb structure body is 31.0 cells/cm.sup.2 or more, and an air-permeability resistance of the partition wall is 4.510.sup.7Pa.Math.s/m.sup.2 or less.

Ceramic honeycomb bodies and methods for then manufacture are provided. The ceramic honeycomb body comprises a bulk density of less than 210 g/L, a geometric surface area (GSA) greater than 93 in.sup.1 (3.66 mm.sup.1), a mechanical integrity factor (MIF) greater than 0.28%, and a back pressure factor (BPF) greater than 0.4 mm.sup.2.

A honeycomb structure including a honeycomb structure body, first plugging portions, and second plugging portions. The honeycomb structure body has a porous partition wall. The first plugging portions are disposed at an outflow side end face of inlet cells and an inflow side end face of outlet cells. The inlet cells are the predetermined cells of the honeycomb structure body. The outlet cells are the residual cells of the honeycomb structure body. The second plugging portions are not fired. The first plugging portions form a checkered pattern at the inflow side end face and the outflow side end face. The number of the second plugging portions is within 3% of the number of cell open ends where the first plugging portions are not formed, on both end faces of the honeycomb structure body.

A honeycomb structure having a hexagonal cross-sectional shape of cells and having specific open cells in which open changing portions are present only in a range of 30 mm or less from the first end face, and the open changing portion satisfies relations of 1|(1(D1/D2))100|70 and 1|(1(D3/D2))100|70. D1 indicates a diameter of an inscribed circle which comes in contact with a peripheral edge of the open end of the cell in the first end face. D2 indicates a diameter of the inscribed circle which comes in contact with the peripheral edge of the open end of the cell in the second end face. D3 indicates a diameter of an inscribed circle which comes in contact with a peripheral edge of the cell in a cross section perpendicular to a direction from the first end face toward the second end face.

In one embodiment, a honeycomb structure formed from ceramic material, or ceramic honeycomb structure, includes at least one outer wall defining a perimeter of the honeycomb structure. A plurality of primary zone partitions and secondary zone partitions may extend in an axial direction of the honeycomb structure and across a width of the honeycomb structure. The primary zone partitions and the secondary zone partitions intersect with one another to divide a radial cross section of the honeycomb structure into a plurality of zones. The primary zone partitions and the secondary zone partitions may have a single-wall thickness with a maximum thickness T.sub.zmax. Each zone may comprise a plurality of channel walls intersecting to subdivide the zone into a plurality of through channels extending in the axial direction of the honeycomb structure, the plurality of channel walls within each zone having a thickness of at least tc and T.sub.Zmax>2t.sub.C.

Honeycomb monolith structure, especially for use as catalyst or support for a catalyst in selective catalytic reduction (SCR) of nitrogen oxides, comprising: a plurality of cell walls defining a plurality of polygonal channels, the plurality of cell walls and channels extending in parallel along a common direction from an entrance end to an outlet end of the structure in the fluid flow direction. The transversal cross section of a polygonal channel has the shape of a convex polygon in closest packing, wherein more than 50% of the internal angels between two adjacent walls of the convex polygon are above 90 degrees and wherein the cell aspect ratio L.sub.L/L.sub.S is greater than 1.5. The monolith structure has an outer row of polygons in shifted direction perpendicular to each other at the two side edges of the monolith which are parallel to the longest direction of the cells/channels.

In the plugged honeycomb structure, 30% or more of first intersection portions in which a first partition wall intersects a second partition wall are first specific intersection portions in which a diameter of a maximum inscribed circle drawn in the first intersection portion is a specific size for a shortest distance between an inflow cell and an outflow cell, and 30% or more of non-first intersection portions other than the first intersection portions are non-first specific intersection portions in which a diameter of a maximum inscribed circle drawn in a non-first intersection portion is a specific size for a shortest distance between the inflow cells or the outflow cells.

A central part of a columnar body in an axis direction parallel to inlet-side flow passages 70H.sub.in and outlet-side flow passages 70H.sub.out includes a first region R.sub.1 where the number of outlet-side flow passages 70H.sub.out adjacent to each inlet-side flow passage 70H.sub.in is N.sub.io1 (N.sub.io1 is any natural number) and a second region R.sub.2 where the number of outlet-side flow passages 70H.sub.out adjacent to each inlet-side flow passage 70H.sub.in is N.sub.io2 (N.sub.io2 is any natural number) and N.sub.io2 N.sub.io1 is satisfied. The outlet-side flow passage 70H.sub.out is not adjacent to another outlet-side flow passage 70H.sub.out, at the first region R.sub.1 and the second region R.sub.2 in the central part of the columnar body in the axis direction.