2016 Volume 56 Issue 7 Pages 1132-1137
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.