| 摘要 |
A catalytic wall-flow monolith 1 for an emission treatment system comprises a porous substrate with first 15 and second 25 faces defining a longitudinal direction therebetween and first and second pluralities of channels each open at a respective face and closed at the other and providing respective inner surfaces. A catalytic material is distributed within the whole or between 85 to 95 % of the length of the porous substrate and a microporous membrane 36 is provided on the channel surfaces. The membrane has pores smaller than soot e.g. 0.1-5 micron and allows a surface soot layer but prevents build-up within the larger substrate pores and thus prevents back-pressure build-up. This allows soot induced backpressure to build within uncoated or thickened coating regions and limits soot collection to manage exothermic effects on regeneration. The layer may extend from the first face for 75 to 95% of a length of the first plurality of channels and may decrease or increase in thickness with distance from the first face. |
