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Applied Catalysis B: Environmental, Vol.3, No.1, 1-11, 1993
Metal Exchanged Ferrierites as Catalysts for the Selective Reduction of No(X) with Methane
Metal ion (Co2+, Mn2+ or Ni2+) exchanged ferrierites are very active catalysts for the reduction of NOx with methane in the presence of excess oxygen. Co-ferrierite yields about twice the nitric oxide conversion compared to Co-ZSM-5 at T> 500 degrees C, previously the most active catalyst reported for this reaction, and Co-ferrierite is more selective in the use of methane. The temperature for maximum nitric oxide conversion is a function of zeolite type and the cation exchanged, and this temperature increases in the following order : Co-ZSM-5 < Co-ferrierite < Mn-ferrierite < Ni-ferrierite. The turnover frequency (TOF) normalized by Co2+ is a function of Co2+ exchange level and increases with the Co2+ loading until it reaches an optimum value, whereas the selectivity for methane decreases with increasing Co2+ loading. The presence of water vapor suppresses the activity of Co-ferrierite; however, under wet conditions, its activity is still much higher than Co-ZSM-5 at T> 500 degrees C.