Catalysis Letters, Vol.104, No.1-2, 72-78, 2005
Catalytic reduction of nitric oxide by hydrogen sulfide over gamma-alumina
The ability of H2S to reduce NO in a fixed bed reactor using a gamma-alumina catalyst was studied with the objective of generating new methods for conversion of NO to N-2. Compared to the homogenous reaction of NO with H2S, the catalyzed reaction showed improved conversions of NO to N-2. Using a gas space velocity of 1000 h(-1) and a feed of 1% NO and 1% H2S in argon, it was found that the conversion of NO to N-2 was complete at 800 degrees C. This result compared to a 38% conversion of NO to N-2 for the homogeneous gas phase reaction at 800 degrees C. At temperatures below 800 degrees C, a short fall in the nitrogen balance was discovered when the gamma-alumina was employed as a catalyst. This discrepancy was explained by conversion of NO to NH3 and subsequent reaction of the NH3 with any SO2 in the system to form ammonium sulfur oxy-anion salts. This suggestion is supported by the finding that when larger amounts of H2S were used relative to NO, more NH3 was formed together in tandem with lower N-2 mass balances. Several reaction pathways have been proposed for the catalytic reduction of NO by H2S.