Production of beta silicon carbide foam filter material used for removing particulates from diesel engine exhaust gases comprises using polyurethane foam with at least two zones of different pore size distribution

摘要

Production of beta silicon carbide foam filter material having specific surface area and comprising at least two zones of different pore size distribution comprises preparing polyurethane foam with at least two zones of different pore size distribution, impregnating foam with thermosetting resin, crosslinking resin by heating, pyrolyzing foam to form carbon foam, activating foam with carbon dioxide, and exposing foam to silicon monoxide vapor. Production of a beta silicon carbide foam filter material having a surface area of at least 5 m2>/g and comprising at least two zones of different pore size distribution comprises preparing a polyurethane foam with at least two zones of different pore size distribution, impregnating the foam with a thermosetting resin, crosslinking the resin by heating, pyrolyzing the foam to form a carbon foam, activating the foam with carbon dioxide at 700-1000[deg]C, and exposing the foam to silicon monoxide vapor. Independent claims are also included for the following: (1) the production of a beta silicon carbide foam filter material having a surface area of at least 5 m2>/g and comprising at least two zones of different pore size distribution by preparing a polyurethane foam with at least two zones of different pore size distribution, impregnating the foam with a suspension of silicon powder in a thermosetting resin, crosslinking the resin by heating, carbonizing the foam and resin and siliciding the resulting carbon by heating to 1600[deg]C or less, and removing residual carbon by oxidation at 650-950 [deg] C; (2) a beta silicon carbide foam having a surface area of at least 5 m2>/g and comprising at least two zones of different pore size distribution, produced by chemical transformation of a porous precursor comprising at least two blocks of different pore size distribution; and (3) a catalytic filter cartridge containing a beta silicon carbide foam filter material having a surface area of at least 5 m2>/g and comprising at least two zones of different pore size distribution and an active phase, the cartridge being surrounded by a solid wall of gas-impermeable material and equipped with an inlet for gases to be filtered and an outlet for gases from which particulates have been removed.