A Modeling and Experimental study on Deactivation of NO oxidation activity on Pt-Pd catalyst with Hydro-Thermal Aging

Rama Krishna  Dadi, Cummins

Rama Krishna Dadi, Ashok Kumar, Rohil Daya, Saurabh Y Joshi, Michael Cunningham and Aleksey Yezerets

Cummins Inc., 1900 McKinley Ave, Columbus, IN 47201, U.S.A.

 

A commercial Pt-Pd catalyst was hydro-thermally treated at different conditions to investigate hydro-thermal stability of NO oxidation. NO oxidation reactor data was collected on catalysts that have been hydro-thermally treated at temperatures of 550°C, 650°C and 700°C. The impact of hydro-thermal aging duration on NO oxidation was studied at each of the hydro-thermal aging temperatures. While NO oxidation activity was studied only under hydro-thermal conditions of 550°C-4h and 550°C-200h, aging duration was changed from 2h to 50 and 100h, respectively for 650°C and 700°C. NO oxidation activity was observed to decrease with increase in Aging duration at all three aging temperatures. Furthermore, rate of decrease in NO oxidation activity with aging duration decreases with increase in Aging duration. The decrease in NO oxidation activity can be attributed to increase in particle size. The decrease in rate of degradation can be owed to stabilization in precious metal dispersion and Turn Over Frequency of NO oxidation. A global kinetic model of NO oxidation was used to estimate the change in NO oxidation rate when subjected to different hydro-thermal aging conditions. Model estimated normalized rates at multiple hydro-thermal aging conditions were used to develop a hydro-thermal aging model of NO oxidation. A Deactivation Model with Residual Activity (DMRA) was developed to capture the impact of hydro-thermal aging temperature and duration on NO oxidation activity. Hydro-thermal aging model used in conjunction with oxidation performance model can serve as hydro-thermal aging-unified global kinetic model for NO oxidation. A global kinetic model that accounts for change in PGM oxidation state with hydro-thermal aging has also been presented. Model that accounts for change in PGM oxidation state with aging has been observed to improve the model’s prediction of NO oxidation. A non-monotonic change in NO oxidation rate with aging duration that could have potentially been observed at aging temperature of 550°C was not explored in this work.