Fluid treatment device having multiple layer honeycomb structure and method of manufacture

15) A fluid treatment device comprising:

• at least two honeycomb layers each comprising a matrix of walls which defines a plurality of parallel, fluid-conducting cells oriented along an axis, said matrix having opposing faces defining inlets and outlets of said cells,
• at least one layer of air space disposed between honeycomb layers along the axis;
• wherein at least one fluid-conducting cell is continuous from one honeycomb layer, across the layer of air space, to a second honeycomb layer.

19) An exhaust gas treatment device comprising at least two honeycomb layers arranged adjacent to each other in a stacked configuration, each honeycomb layer comprising a matrix of ceramic walls that define a plurality of parallel, gas-conducting cells along an axis, and opposing faces defining inlets and outlets of said cells, and a peripheral portion including an outer skin,

• wherein the faces of adjacent honeycomb layers are axially spaced apart;
• and
• wherein at least one of the faces of the honeycomb layers is concave.

25) A method for manufacturing a fluid treatment device comprising the steps of:

• providing a monolith honeycomb structure having a honeycomb matrix defining a plurality of parallel, fluid-conducting cells oriented along an axis;
• removing a portion of said matrix along said axis to define axially spaced apart honeycomb layers separated by air space wherein the peripheral portions of adjacent honeycomb layers are integrally connected to one another, and;
• firing said monolith honeycomb structure.

31) A fluid treatment device comprising:

• a monolithic honeycomb structure having an overall axial length between first and second ends, the structure comprising a matrix of walls which defines a plurality of parallel, fluid-conducting cells oriented in an axial direction, wherein a first plurality of continuous walls form uninterrupted cells in a peripheral portion, extending substantially the entire overall axial length and wherein a second plurality of walls form discontinuous cells, wherein the discontinuous cells are open to a common recess within the structure between the first and second ends.

33) A fluid treatment device comprising:

• at least two honeycomb layers arranged in a stacked configuration, each layer including a matrix of walls that defines a plurality of parallel, fluid-conducting cells oriented along an axis, each layer having a leading edge face and a trailing end face;
• at least one layer of air space disposed between honeycomb layers along the axis;
• wherein at least one honeycomb layer has a coating of catalytic material at the leading edge face and does not have a coating of catalytic material at the trailing edge face.