(340d) Multipollutant Emissions Control with Emx™ Lean Nox Trap Catalyst Technology

EMx is principally known as a catalytic
technology for controlling combustion-generated NOx emissions. However, at its
heart there is a potent oxidation catalyst and other basic surface chemistry components
capable of 99% reduction of CO, organic compounds, SOx and high performance
removal of particulate matter. In its basic configuration EMx consists of two
active components. The first is a regenerable SOx guard bed. The second is the
lean NOx trap. As exhaust gases pass through the system SO₂ is
oxidized to sulfate and trapped on the guard bed. NOx is then oxidized to NO₂
and trapped on the surface of the NOx trap. Both of these units are
periodically regenerated with a stream of dilute hydrogen, releasing the NOx as
molecular nitrogen and the sulfur as SO₂ (which can be collected and
removed from the gas stream).  However, while NOx and SOx are being adsorbed
other processes are also taking place. CO and hydrocarbons are readily
oxidized, often leading to non-detectable levels at the system exhaust. Also,
significant reductions in particulate matter ? particularly the condensable
inorganic fraction ? have been measured, suggesting a mechanism for soot
oxidization. This points the way for further developments in the technology
with positive implications for airshed regions such as California's South Coast Basin and San Joaquin Valley, and Texas' greater Houston area.