Manganese-based catalysts
have shown great potential for use as
a hydrocarbon reductant for NO
x
reduction
(HC-SCR) at low temperatures if their catalytic stability could be
further maintained. The effect of CeO
2
as a promoter and
catalyst stability agent for activated carbon supported MnO
x
was investigated during low temperature deNO
x
based on a C
2
H
4
reductant.
The modern characterization technology could provide a clear understanding
of the activity observed during the deNO
x
tests. When reaction temperatures were greater than 180 °C
and with ceria concentrations more than 5%, the overall NO conversion
became stable near 70% during long duration testing. In situ DRIFTS
shows that C
2
H
4
is adsorbed on the Mn
3
Ce
3
/NAC catalysts to generate hydrocarbon activated intermediates,
R-COOH, and the reaction mechanism followed the E-R mechanism. The
stability and the analytical data pointed to the formation of stable
oxygen vacancies within Ce
3+
/Ce
4+
redox couplets
that prevented the reduction of MnO
2
to crystalline Mn
2
O
3
and promoted the chemisorption of oxygen on
the surface of MnO
x
-CeO
x
structures. Based on the data, a synergetic mechanism model
of the deNO
x
activity is proposed for
the MnO
x
-CeO
x
catalysts.
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