Decomposition and selective catalytic reduction of NO by propane on CuZSM-5 zeolites: a mechanistic study

NO decomposition and selective catalytic reduction (SCR) of NO by propane i n oxygen were compared over Cu-ZSM-5 with various Si/Al ratios and extent o f exchange. It was established that the turnover frequency (TOF) values ref erred to copper ions species characterized by NO desorption, are independen t of the Si/Al ratio and the extent of exchange. The presence of propane an d oxygen accelerates N-2 formation and higher conversion can be reached at lower temperature. TPD experiments indicate that the Cu2+(O)(NO)(NO2) surfa ce complex, which is formed as an intermediate in the decomposition of NO, is not the active pathway in SCR. In SCR of NO by propane in the presence o f oxygen, the first step is Cu(I) to Cu(II) conversion by oxygen. NO2 forma tion is facilitated by Cu(II) species, which react with propane forming a n itrito-propane compound. Its result in N-2 formation at a lower temperature than what is required for decomposition of NO. (C) 2000 Elsevier Science B .V. All rights reserved.