Hydrocarbon and NO trap/release characteristics of Pd/ and Ag/zeolites with US-DRIVE Protocol

Andrew  Binder, Oak Ridge National Laboratory

The draft form US-DRIVE Trapping Protocol was used to evaluate the hydrocarbon and NOx trapping potential for BEA and ZSM-5 zeolites with ion-exchanged Pd or Ag.  All materials underwent 700°C degreening prior to exposure to the protocol gas stream which included NO, ethylene, toluene, and decane as measured trapping species as well as common exhaust gasses CO, H₂O, O₂, CO₂, and H­₂.  Evaluation showed that all materials were effective at trapping hydrocarbon species, with none reaching full capacity after 30 minutes of exposure.  While these traps showed low potential for NOx, all materials were able to trap over 40% of hydrocarbon species in the first 3 minutes of exposure and over 70% in the first 3 minutes for Ag/ZSM-5.  On average Ag/zeolite materials were capable of higher storage efficiency while Pd/zeolite materials showed increased capability to oxidize adsorbed species directly at elevated temperatures.

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