SELECTIVE CATALYTIC REDUCTION OF NITRIC-OXIDE BY PROPANE IN OXIDIZINGATMOSPHERE OVER COPPER-EXCHANGED ZEOLITES

Selective catalytic reduction of nitric oxide with propane and oxygen was investigated on Cu-exchanged ZSM-5, mordenite, X-type and Y-type z eolites at temperatures in the range of 200 to 600-degrees-C. Catalyti c activities of Cu-X and Cu-Y are negligible, activity of Cu-mordenite moderate, and that of Cu-ZSM-5 very high, converting > 90% of nitric oxide to nitrogen at 400-degrees-C and at a space velocity of 102 000 h-1. Effects of space velocity, nitric oxide concentration, C3H8/NO ra tio, oxygen concentration, and water vapor on the activities of Cu-ZSM -5 and Cu-mordenite were investigated. Nitric oxide conversion decreas es with increasing space velocity, decreasing propane and nitric oxide concentrations, and decreasing propane/NO ratio. Water vapor decrease s the activity significantly at all temperatures. At temperatures abov e 400-degrees-C, propane oxidation by oxygen is a significant competin g reaction in decreasing the selectivity for nitric oxide reduction. T he results indicate that Cu-ZSM-5 is a promising catalyst for selectiv e catalytic reduction of nitric oxide by hydrocarbons.