Catalytic Decomposition of Pyridine with Goethite-Rich Limonite in the Coexistence of Fuel Gas or Coke Oven Gas Components

Abstract

Catalytic performance of limonite in the decomposition of 100 ppmv pyridine (C₅H₅N) in the coexistence of fuel gas or coke oven gas (COG) components has been studied mainly with a cylindrical quartz reactor at 750–850°C under a high space velocity of 51000 h⁻¹ to develop a novel hot gas cleanup method of removing the nitrogen in tar as N₂. The limonite catalyst achieves the almost complete decomposition of C₅H₅N in He at 500–850°C and gives a high N₂ yield of more than 85 N% at 500°C. When the decomposition run is performed in the presence of fuel gas or COG components, the coexistence of 20% CO/10% H₂ at 750°C or 50% H₂/30% CH₄/5% CO at 850°C deactivates the limonite with remarkable formation of deposited carbon. On the other hand, the addition of a small amount of H₂O or CO₂ to these atmospheres can improve the catalytic activity without carbon deposition. When 3% H₂O or 10% CO₂ is added to 20% CO/10% H₂, C₅H₅N conversion and N₂ yield at 750°C become 80–95% and 65–80 N%, respectively, and the extent of the improvement is larger with the CO₂ than with the H₂O. The addition of 5% CO₂ to 50% H₂/30% CH₄/5% CO also restores the conversion or the yield at 850°C to the high level of about 90% or 60–70 N%, respectively, and both values at 950°C are comparable to those at 500°C in inert gas.