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One of the main drawbacks of the NOx adsorber technology vs. the other leading approach for high level NOx conversion, namely selective catalytic reduction, is its high sensitivity to sulfur. In spite of the likely availability of ultra-low sulfur fuel and protecting devices like sulfur traps, and furthermore taking into consideration additional sulfur sources such as engine oil and lubricants, a desulfurization strategy will be essential to the commercial implementation of NOx adsorber catalysts on diesel vehicles. The results presented in this paper were obtained on NOx adsorbers with proven thermal durability and efficiency in diesel engine exhaust. They show NOx performance recovery following severe sulfur poisoning, after desulfation under temperature and air/fuel mixture conditions compatible with diesel engine operation. In addition, different desulfurization tactics, tested on a synthetic gas bench simulating diesel exhaust, are depicted and discussed.

Dual-monolith converters containing Pd-only catalysts followed by Pt/Rh three-way catalysts (TWCs) provide effective emission solutions for NLEV and Tier IIa close-coupled dual-bank V-8 applications due to optimal hydrocarbon and NOx light-off, transient NOx control, and balance of precious metal (PGM) usage. Dual-catalyst [Pd +Pt/Rh] systems on a 5.3L V-8 LEV light truck vehicle were characterized as a function of PGM loading, catalyst technology, and substrate cell density. NLEV hydrocarbon emission control of the 6500 lb vehicle was optimal using dual 1.2L converters with each containing front ceria-free Pd catalysts coupled with rear Pt/Rh TWCs. Advanced non-air prototype calibrations coupled with reduced catalyst washcoat mass on 600cpsi/4mil substrate resulted in minimal Pd usage of ∼0.02 toz/vehicle due to achieving catalyst inlet temperatures of 350-400°C in <10 sec on both banks of the V-8 engine.