Emission Control System using a Multi-Function Catalyzing Filter

Abstract

A multi-function filter is provided for use in emission control systems, for example, on the exhaust gas from an internal combustion engine. The filter has a substrate constructed using bonded fiber structures, which cooperate to form a highly uniform open cell network, as well as to provide a uniform arrangement of pores. The substrate typically is provided as a wall-flow honeycomb structure, and in one example, is manufactured using an extrusion process. In this way, the substrate has many channel walls, each having an inlet surface and an outlet surface. The inlet surface has a uniform arrangement of pores that form a soot capture zone, where soot and other particulate matter is captured from an exhaust gas. A gas conversion catalyst is disposed inside the channel wall, where one or more pollutants in the exhaust gas are converted to less harmful substances. Because of the uniform pore structure and open cell arrangement inside the channel wall, the filter is capable of being heavily loaded with catalyst, while avoiding undue increase in backpressure to the internal combustion engine.

1 . A multi-function wallflow filter, comprising:
 an arrangement of bonded fiber structures forming inlet and outlet channels that are separated by respective channel walls;   a soot capture zone on at least some of the channel walls constructed to enable a highly uniform loading of soot;   a gas-conversion zone inside at least some of the channel walls constructed to enable a highly uniform loading of a gas conversion catalyst;   a catalyst in the gas-conversion zone for converting an undesirable exhaust gas to a more desirable exhaust gas.   
     
     
         2 . The multi-function filter according to  claim 1 , wherein the soot capture zone comprises the bonded fiber structures arranged to form a highly uniform set of pores that are exposed at the surface of the channel walls of the multi-function filter. 
     
     
         3 . The multi-function filter according to  claim 1 , wherein the gas-conversion zone comprises the bonded fiber structures arranged to form a highly uniform set of pores inside the channel walls of the multi-function filter. 
     
     
         4 . The multi-function filter according to  claim 1 , wherein the bonded fiber structures are one selected from the group consisting of: individual fibers bonded at intersecting nodes, fiber bundles cooperating with each other or individual fibers, and elongated polycrystalline fiber-like structures. 
     
     
         5 . The multi-function filter according to  claim 1 , wherein the bonded fiber structures have a fiber composition comprising a metal, a ceramic, SiC, AlO3, or mullite. 
     
     
         6 . The multi-function filter according to  claim 1 , wherein the channels are arranged in a honeycomb pattern. 
     
     
         7 . The multi-function filter according to  claim 1 , wherein the channels are extruded in a honeycomb pattern. 
     
     
         8 . The multi-function filter according to  claim 1 , wherein the soot capture zone consists of side walls of inlet channels. 
     
     
         9 . The multi-function filter according to  claim 1 , wherein the soot capture zone comprises a cake filter on the side wall of respective inlet channels. 
     
     
         10 . The multi-function filter according to  claim 1 , wherein the soot capture zone extends into the channel wall. 
     
     
         11 . The multi-function filter according to  claim 1 , wherein the soot capture zone comprises side walls of inlet channels, and the side walls further comprise fibers arranged according to frictional contact with die openings of an extrusion machine. 
     
     
         12 . The multi-function filter according to  claim 1 , wherein the gas-conversion zone comprises an open cell network arranged to generate a tortuous flow path for an exhaust gas. 
     
     
         13 . The multi-function filter according to  claim 1 , wherein the gas-conversion zone comprises a substrate structure of bonded fibers or fiber-like structures. 
     
     
         14 . The multi-function filter according to  claim 1 , wherein the gas-phase zone comprises more than about 20 grams/cu. ft. of the gas-conversion catalyst. 
     
     
         15 . The multi-function filter according to  claim 1 , further comprising a second gas-conversion zone having a second gas-conversion catalyst. 
     
     
         16 . The multi-function filter according to  claim 15  wherein the first gas conversion zone is adjacent to the gas inlet of the multifunction filter and the second gas conversion zone is adjacent to the outlet of the multifunction filter. 
     
     
         17 . The multi-function filter according to  claim 15 , wherein the first gas conversion zone is inside at least some of the channel walls, and the second gas conversion zone comprises side walls of at least some of the outlet channels. 
     
     
         18 . The multi-function filter according to  claim 1 , wherein the soot capture zone and the gas conversion zone coexist in the same area of the multi-function filter. 
     
     
         19 . An emission control system for an internal combustion engine, comprising:
 an inlet for receiving an exhaust gas, the exhaust gas comprising particulate matter and an undesirable pollutant gas;   a fibrous substrate comprised of an organized arrangement of bonded fiber-structures for receiving the exhaust gas;   a particulate matter filtering zone on the fibrous substrate for collecting the particulate matter;   a gas conversion zone in the fibrous substrate that is loaded with a gas-conversion catalyst selected to convert the pollutant gas to a more desirable gas; and   an engine control system for adjusting the internal combustion engine according to measured performance.   
     
     
         20 . The emission control system according to  claim 19 , further including a second gas conversion zone in the fibrous substrate that is loaded with a second gas-conversion catalyst selected to convert a second pollutant gas to a more desirable gas. 
     
     
         21 . The emission control system according to  claim 19 , further including a regeneration catalyst in the particulate matter filtering zone for assisting in conversion of soot during a regeneration process 
     
     
         22 . The emission control system according to  claim 19 , wherein the fibrous substrate is constructed from individual fibers bonded at intersecting nodes;
 fiber bundles cooperating with each other or individual fibers; or elongated polycrystalline fiber-like structures.   
     
     
         23 . A multi-function filter assembly, comprising:
 an arrangement of bonded fiber structures forming a substrate;   a single can for holding the substrate, the can having an inlet and an outlet;   a plurality of input and output channels in the substrate and separated by respective channel walls to form a wall-flow arrangement;   a washcoat material disposed in the filter substrate; and   a catalyst material disposed on the washcoat.   
     
     
         24 . The emission control system according to  claim 23 , wherein the substrate is constructed from individual fibers bonded at intersecting nodes; fiber bundles bonded to other fiber bundles or individual fibers; or elongated polycrystalline fiber-like structures bonded together. 
     
     
         25 . The multi-function filter assembly according to  claim 23 , wherein the substrate exhibits an insignificant level of channeling effect during soot loading. 
     
     
         26 . The multi-function filter assembly according to  claim 23 , wherein the substrate exhibits an insignificant level of channeling effect during soot unloading. 
     
     
         27 . The multi-function filter assembly according to  claim 23 , wherein the washcoat and catalyst, in the aggregate, are loaded to more than 10 gram/cu. ft in the substrate. 
     
     
         28 . The multi-function filter assembly according to  claim 23 , wherein the washcoat and catalyst, in the aggregate, are loaded to more than 30 gram/cu. ft in the substrate. 
     
     
         29 . The multi-function filter assembly according to  claim 23 , wherein the washcoat and catalyst, in the aggregate, are loaded to more than 50 gram/cu. ft in the substrate. 
     
     
         30 . The multi-function filter assembly according to  claim 23 , wherein the washcoat and catalyst, in the aggregate, are loaded to up to 400 gram/cu. ft in the substrate.