Hydrothermal degreening and ageing procedures were applied to a tri-metal (Pt-Pd-Rh) fully formulated lean NOx Trap catalyst to evaluate the effects of thermal stress on the performances and structural properties. X-ray absorption fine structure (XAFS) analysis revealed that the average size of the platinum particles was the same after degreening and ageing treatments. The formation of a new phase of alloyed Pt-Pd was observed to increase with the thermal load. The size of the ceria particles also increased after the ageing treatment. NOx storage capacity experiments revealed a substantial decrease of the concentration of active NOx storage sites which correlated with both ageing and degreening protocols. The performances of the treated catalyst were evaluated through spatially resolved (SpaciMS) lean-rich cycles. During the lean phase, the impact of the decrease in storage sites was significant on the aged sample, where an enlargement of the area required to achieve full storage was observed. On the other hand, the regeneration functionalities did not appear to be particularly affected by ageing. Rather, the aged sample showed a decrease of oxygen storage capacity (OSC), which promoted a lower reductant consumption and therefore a quicker and more efficient reduction process. On the other hand, the different distributions of adsorbed species by the end of the lean phase produced greater spread presence of NH3 and NOx slip along the channels of the aged sample during the reduction.
Bibliographical noteFunding Information:
The work reported was supported by Ford Motor Company. The authors wish to acknowledge the Diamond Light Source for provision of beamtime (SP15151). The x-ray photoelectron (XPS) data collection was performed at the EPSRC National Facility for XPS (?HarwellXPS?), operated by Cardiff University and UCL, under Contract No. PR16195.
The work reported was supported by Ford Motor Company . The authors wish to acknowledge the Diamond Light Source for provision of beamtime (SP15151). The x-ray photoelectron (XPS) data collection was performed at the EPSRC National Facility for XPS (“HarwellXPS”), operated by Cardiff University and UCL, under Contract No. PR16195.
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- Lean NOx trap
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Student thesis: Doctoral Thesis › Doctor of EngineeringFile