Catalytic filter based on silicon carbide (β-SiC) for combustion of soot derived from exhaust gases from an internal combustion engine
View Patent ↗This invention relates to β-SiC foam parts with a specific surface area preferably equal to at least 5 m 2 /g and with at least two zones A and B with a different cellular porosity distribution, wherein the parts were made by chemical transformation of a porous precursor medium comprising at least two blocks A′ and B′, each having a different cellular porosity distribution, and in that the at least two zones A and B are derived from the chemical transformation of the two blocks A′ and B′. This foam, optionally after deposition of an active layer, may be used as a filter medium in cartridges designed for the purification of exhaust gases. The invention also relates to manufacturing processes for preparing such a filter medium.
1. A β-SiC foam part having a specific surface area equal to at least 5 m 2 /g, and comprising at least two zones A and B, each having a different porosity distribution, wherein the foam part was made by chemical transformation of a porous precursor medium comprising at least two blocks A′ and B′, each having a different porosity distribution, and wherein the at least two zones A and B are derived from the chemical transformation of the at least two blocks A′ and B′.
2. The β-SiC foam part according to claim 1 , wherein the foam has an average pore size ranging from 500 μm to 4000 μm.
3. The β-SiC foam part according to claim 2 , wherein the foam has an average pore size ranging from 800 μm to 4000 μm.
4. The β-SiC foam part according to claim 3 , wherein the foam has an average pore size ranging from 900 μm to 3000 μm.
5. The β-SiC foam part according to claim 4 , wherein the foam has an average pore size ranging from 900 μm to 1800 μm.
6. The β-SiC foam part according to claim 1 , wherein the density of the foam part ranges from 0.05 g/cm 3 to 0.5 g/cm 3 .
7. The β-SiC foam part according to claim 1 , wherein the density of the foam part ranges from 0.1 g/cm 3 to 0.2 g/cm 3 .
8. A β-SiC foam part prepared using a process comprising:
(a) preparing a precursor medium comprising a carbonizable foam having an open cellular porosity and a predefined porous distribution, the precursor medium being impregnated with a hardening resin;
(b) cross-linking the resin;
(c) pyrolizing the foam to form carbon foam;
(d) activating the carbon foam; and
(e) exposing the activated carbon foam to an SiO vapor to form silicon carbide foam, wherein
the beta-SiC foam comprises at least two zones, each of said at least two zones having a different porosity distribution.