Mechanisms of NH₃ generation using LNT-like catalysts have been
studied in a bench reactor over a wide range of temperatures, flow
rates, reformer catalyst types and synthetic exhaust-gas
compositions. The experiments showed that the on board production
of sufficient quantities of ammonia on board for SCR operation
appeared feasible, and the results identified the range of
conditions for the efficient generation of ammonia. In addition,
the effects of reformer catalysts using the water-gas-shift
reaction as an in-situ source of the required hydrogen for the
reactions are also illustrated. Computations of the NH₃ and NOx
kinetics have also been carried out and are presented. Design and
impregnation of the SCR catalyst in proximity to the ammonia source
is the next logical step.
A heated synthetic-exhaust gas flow bench was used for the
experiments under carefully controlled simulated exhaust
compositions. Operating conditions include rich-lean cycles so that
the transient production of NH₃ and the reduction of NOx could be
monitored. The bench offered significant flexibility and separate
control over the wide ranges of temperatures, flow rates, and the
compositions of the mixture. Gas concentrations were measured by
Fourier Transform Infrared (FT-IR) Spectroscopy.