| CPC F01N 3/0222 (2013.01) [B01D 46/24491 (2021.08); B01D 46/24492 (2021.08); B01D 46/2484 (2021.08); B01D 46/62 (2022.01); B01D 53/9431 (2013.01); F01N 3/2066 (2013.01); F01N 13/009 (2014.06); B01D 46/2418 (2013.01); B01D 46/2425 (2013.01); B01D 46/2429 (2013.01); B01D 53/9418 (2013.01); B01D 53/9422 (2013.01); B01D 2251/2067 (2013.01); B01D 2258/01 (2013.01); B01D 2279/30 (2013.01); F01N 3/023 (2013.01); F01N 3/0231 (2013.01); F01N 3/029 (2013.01); F01N 3/0814 (2013.01); F01N 3/0871 (2013.01); F01N 3/206 (2013.01); F01N 3/208 (2013.01); F01N 2330/06 (2013.01); F01N 2330/48 (2013.01); F01N 2610/1453 (2013.01)] | 19 Claims |

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1. An exhaust treatment apparatus for treating an exhaust stream flowing through an exhaust line housing in a downstream direction from an upstream location of the exhaust line housing to a downstream location, the exhaust treatment apparatus comprising:
a first particulate filter;
an SCR unit disposed downstream of the first particulate filter; and
a second particulate filter disposed downstream of the SCR unit;
wherein the first particulate filter, the SCR unit, and the second particulate filter are disposed serially in the exhaust line housing and are configured to allow the exhaust stream to flow serially through the first particulate filter, subsequently through the SCR unit, and subsequently through the second particulate filter wherein the first particulate filter is comprised of a first honeycomb body comprised of intersecting porous ceramic walls comprising a first bulk average porosity of 40-65% as measured by mercury porosimetry, and the second particulate filter is comprised of a second honeycomb body comprised of intersecting porous ceramic walls comprising a second bulk average porosity of 35-55% as measured by mercury porosimetry.
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