A combined transient in situ FTIR and flow reactor study of NO_X storage and reduction over M/BaCO_3/Al_2O_3 (M=Pt,Pd or Rh) catalysts

摘要

Transient in situ DRIFTS and flow-reactor experiments were performed to study the storage and reduction of NO_X over Pd/BaCO_3/Al_2O_3,and Rh/BaCO_3/Al_2O_3 samples using CO,H_2,C_3H_6,or C_3H_8 as the reducing agent.The DRIFTS results show that exposure of the examined samples to NO_2 results in the formation of nitriteitrate peaks over alumina and barium and that the reduction of stored NO_X is influenced by the type of precious metal and reducing agent.Using CO as the reductant results in a lower NO_X reduction capacity for Pt/BaCO_3/AL_2O_3 compared with Pd-and Rh-based samples,whereas H_2 shows a significant ability to reduce the stored NO_X on all samples examined.In addition,the reduction with CO and C_3H_6 proceeds via the formation of isocyanate species over both barium and alumina sites.The intensity of barium-isocyanate species for Pt/BaCO_3/Al_2O_3 is significantly lower than the corresponding intensity for the Pd-and Rh-based samples,suggesting that the interaction between barium and Pt is lower than the corresponding interaction in the Pd/BaCO_3/Al_2O_3 and Rh/BaCO_3/Al_2O_3 samples.