A ceramic honeycomb body having intersecting walls that form channels extending axially from a first end face to a second end face and plugs to seal the channels at least at one of the first end face and the second end face. The plugs include a first active component, such as a catalytically active component or a chemically active component, of the plug structure, wherein the intersecting walls comprise no first active component and optionally have a second active component of the wall structure or disposed on the walls. Included are methods of making the ceramic honeycomb body having plugs of the first active component and walls with no first active component.

In a porous body, a surface layer thickness Ts takes a relatively small value satisfying P≧0.54 Ts (formula (1)), the surface layer thickness Ts being derived by a microstructure analysis using the porous-body data that is prepared through three-dimensional scanning of a region including a surface (inflow plane 61) of the porous body. Here, P denotes a porosity [%] of the porous body, and 0%<P<100% and 0 μm<Ts are assumed. The surface layer thickness Ts is derived as a distance in a thickness direction (X direction) between a surface-layer region start plane 92 in which a straight-pore opening ratio becomes 98% or less for the first time and a surface-layer region end plane 93 in which the straight-pore opening ratio becomes 1% or less for the first time.

A porous body is provided with enhanced fluid transport properties that is capable of performing or facilitating separations, or performing reactions and/or providing areas for such separations or reactions to take place. The porous body includes at least 80 percent alpha alumina and has a pore volume from 0.3 mL/g to 1.2 mL/g and a surface area from 0.3 m.sup.2/g to 3.0 m.sup.2/g. The porous body further includes a pore architecture that provides at least one of a tortuosity of 7.0 or less, a constriction of 4.0 or less and a permeability of 30 mdarcys or greater. The porous body can be used in a wide variety of applications such as, for example, as a filter, as a membrane or as a catalyst carrier.

A honeycomb structure body has an inner side base section and an outer side base section having a cylindrical shape. Inner side cells are formed in the inner side base section at a constant cell density. Outer side cells are formed in the outer side base section. A cell density of the outer side cells varies a radius direction. The outer side cells are formed on the basis of a relational equation of y=a(x−b).sup.n+c, where x is a distance on the outer side base section measured from a central point on a radial cross section, y indicates the number of the outer side cells per one cm.sup.2 at the distance x, a is a negative constant, b is a radius of the inner periphery of the outer side base section, c is the number of the inner side cells per one cm.sup.2, and n is a degree.

A porous ceramic honeycomb body (10) including intersecting walls that form channels (22) extending axially from a first end face to a second end face and layered plugs (62) comprised of a first layer (64) disposed on channel walls and a second layer (66) disposed inward toward an axial center of each respective channel on the first layer. The plugs seal at least one of a first portion of the channels at the first end face and a second portion of channels at the second end face of the porous ceramic honeycomb body.

A honeycomb structure has partition walls defining a plurality of polygonal cells which become through channels for a fluid, a structure end face vertical to an axial direction has at least two cell regions possessing mutually different cell structures and surrounded by circumferential portions, and in the cell regions adjacent to each other, to first partition walls of a first cell structure of one first cell region, second partition walls of a second cell structure of the other or second cell region are tilted.

A honeycomb structure includes a honeycomb structure body including porous partition walls defining a plurality of cells serving as fluid passages extending from an inflow end face to an outflow end face. The partition walls have a porosity of 45 to 65%; the open frontal area of the pores having an equivalent circle diameter of 10 μm or more, of the pores open on the surface of each partition wall, is 20 to 50%; the pore density of the pores having an equivalent circle diameter of 10 μm or more is 200 to 1,000 pores/mm.sup.2; the median opening diameter of the pores having an equivalent circle diameter of 10 μm or more is 40 to 60 μm; the circularity of the pores having an equivalent circle diameter of 10 μm or more is 1.8 to 4.0; and the partition walls have a wet area of 16,500 μm.sup.2 or more.

A honeycomb structure comprising: a honeycomb structure body that includes a plurality of porous partition walls and intersection parts, and a catalyst layer, wherein the porosity of the partition wall is 20 to 70%, the average pore diameter of the pores in the partition wall is 1 to 60 μm, a plurality of the partition walls includes a notched partition wall having a recessed part in which at least one end is notched, the ratio of the notched partition wall in the partition walls is 1 to 100%, the recessed part of the notched partition wall has a depth of 10 to 200% of the standard length, and the recessed part of the notched partition wall is a part having a width of 33 to 100% of the standard width.

The manufacturing method of the honeycomb structure includes a raw material preparing step of adding the powder of porous silica as the inorganic pore former to a forming raw material and kneading the forming raw material to prepare the kneaded forming raw material, an extruding step of extruding the obtained forming raw material to form a honeycomb formed body, and a firing step of firing the extruded honeycomb formed body to form a honeycomb structure containing a cordierite component, and an amount of oil to be absorbed by the porous silica to be added to the forming raw material is in a range of 50 to 190 ml/100 g, and a BET specific surface area of the porous silica is in a range of 340 to 690 m.sup.2/g.

A process for producing a ceramic catalyst involves the steps of: a) providing functional particles having a catalytically inactive pore former as a support surrounded by a layer of a catalytically active material, b) processing the functional particles with inorganic particles to form a catalytic composition, c) treating the catalytic composition thermally to form a ceramic catalyst, wherein the ceramic catalyst comprises at least porous catalytically inactive cells which are formed by the pore formers in the functional particles, which are embedded in a matrix comprising the inorganic particles, which form a porous structure and which are at least partly surrounded by an active interface layer comprising the catalytically active material of the layer of the functional particles.

An SCR catalyst produced in by this method has an improved NO.sub.x conversion rate compared to a conventionally produced SCR catalyst.