An alumina-based LNT is being developed through
laboratory studies, for diesel vehicle applications. This
LNT provides high NOx conversion efficiency at low
temperature (150 to 350°C, especially below 200°C),
which is very important for the exhaust-gas aftertreatment
of diesel passenger vehicles. Addition of 2 to 4
wt% of alkaline-earth metal oxide or other metal oxides
to the alumina LNT formulation improves NOx reduction
activity at the high end of its active temperature window.
More significantly, the alumina-based LNT can undergo
the de-SOx process (the process of removing sulfur from
the catalytic surfaces) very efficiently: within 1 minute at
the relatively low temperature of 500 to 650°C under
slightly rich conditions (lambda = 0.98 to 0.987). Such a mild
de-SOx process imposes minimal thermal exposure,
causing almost no thermal damage to the LNT, and
helps minimize the associated fuel penalty. The aluminabased
LNT could thus provide a solution to the current
LNT durability issue caused by sulfur poisoning and the
need to aggressively de-SOx at high temperature.
Possible applications of the alumina-based LNT for
diesel and HCCI were studied in the laboratory. A
multiple (staged) alumina-based LNT system was tested
in the lab that provides high NOx reduction activity over a
wide temperature range (150 to 550°C) and still
maintains the unique efficient de-SOx process of the
alumina-based LNT resulting in minimal thermal damage
to the LNT. Lab results also suggest that the aluminabased
LNT would work well with the catalyzed DPF (for
diesel) and the TWC (for an HCCI exhaust system).
Further studies, extending the laboratory experiments to
engine and vehicle evaluations, are needed to fully
assess the potential of the alumina-based LNTs.